I NRYCOMSTOCK -J#^^ f> LibKil QoAe THE SPIDER BOOK WEB OF METARGIOPE TRIFASCIATA )L 57- % THE SPIDER BOOK A MANUAL FOR THE STUDY OF THE SPIDERS AND THEIR NEAR RELATIVES, THE SCORPIONS, PSEU- DOSCORPIONS, WHIP-SCORPIONS, HARVESTMEN, AND OTHER MEMBERS OF THE CLASS ARACH- NIDA, FOUND IN AMERICA NORTH OF MEXICO, WITH ANALYTICAL KEYS FOR THEIR CLASSIFICA- TION AND POPULAR ACCOUNTS OF THEIR HABITS Bv JOHN HENRY COMSTOCK PROFESSOR OF ENTOMOLOGY IN CORNELL UNIVERSITY Garden City New York DOUBLEDAY, PAGE & COMPANY 1913 Copyright, 1912, by DOUBLEDAY, PAGE & COMPANY All rights reserved, including that of translation into Foreign Languages, including the Scandinavian TO BURT GREEN WILDER WHO FIRST AWAKENED MY INTEREST IN SPIDERS; AND WHO THROUGHOUT AN INTIMATE ASSOCIATION OF MORE THAN FORTY YEARS, FIRST AS MY TEACHER AND LATER AS A COLLEAGUE, HAS NEVER WEARIED IN HELPFUL ASSISTANCE, THI^ BOOK IS AFFECTIONATE IV DEDICATED PREFACE The object of the work here offered to the public is to serve as an introduction to the study of a much neglected group of animals, the Arachnida. While the list of Americans who have contributed to our knowledge of insects is a very long one, those who have seriously studied the closely allied Arachnida in this country barely number a score; and the publications of these workers have been, of necessity, largely of a pioneer nature and fragmentary. Comparatively little of that which has been pub- lished is adapted to the needs of the beginning student. There have appeared in this country, however, a few works designed for beginners; among these are two small books by Kmerton, "The Structure and Habits of Spiders," published in 1878, and "The Common Spiders of the United States," pub- lished in 1902, two excellent works which have done much to popularize a knowledge of spiders. The great work of McCook, "American Spiders and Their Spinningwork" (1889-93), ls well adapted to awaken an interest in this subject; but its rarity and cost prevent its general use. The analytical tables published by Banks in the American Naturalist, in the volumes for 1900, 1901, and 1905, have been very useful. A few writers, as Dr. Wilder and Mrs. Treat, have published magazine articles on particular species. This practically completes the list of popular works on this subject published in this country. The papers on the classification of American spiders are far more numerous, and many of them have been published abroad; so also, the works treating of the structure of spiders are many and are largely foreign. A list of all of the publications quoted in the following pages is given in an appendix. In concluding this reference to the literature of the subject, 1 wish to make special mention of the work from which I have derived more help than from any other; this is the " Histoire Naturelle des Araignees," by Eugene Simon, published in Paris (1802-1903). Special acknowledgment is due to the authorities of Cornel' vii Pref ace University, whose liberal grants for the purchase of books and of specimens have made possible the prosecution of my studies in a satisfactory manner. Important aid has been rendered by several specialists. Mr. Peckham has determined specifically a considerable part of the large collection of Attidae in the Cornell University museum. Mr. Emerton has also determined many species of spiders. And Mr. Banks has rendered assistance frequently throughout the preparation of the work in the determination of both spiders and other arachnids. Several students, who have worked under my direction, have contributed in an important way to the advancement of the work; notably Prof. R. V. Chamberlin, by studies of the Lycosidae; Prof. C. R. Crosby, by studies of the Erigoninae; Miss Effie A. Read, by help in the preparation of the key to the genera of the Attidae; Mr. R. A. Cushman, by studies of the external reproductive organs of the Argiopidae; Dr. J. A. Nelson, by the preparation of many palpi of male spiders; and Mr. J. T. Lloyd, by testing and suggesting changes in some of the analytical keys. Early in the progress of the work on this book I had the good fortune to secure, by purchase for Cornell University, the col- lection of Dr. William H. Fox of Washington. This contained nearly 250 named species of spiders; and as the identification of the specimens had been confirmed by the late Dr. George Marx, the collection formed a very important addition to the Cornell University museum. And I am indebted to Doctor Fox for in- formation regarding certain specimens in the collection made by him. Contributions of specimens have been received from many persons; and large numbers of specimens have been received from each of the following: Prof. C. R. Crosby, Mr. Paul Hayhurst, and Dr. J. A. Nelson. To Dr. B. G. Wilder I am indebted for my first interest in spiders, acquired during my undergraduate days, and for placing at my disposal, in later years, all of his notes on spiders. The photographs from which a large part of the illustrations were made were taken by myself, except in those cases where credit to others is given. Some of the drawings, especially those in the chapter on external anatomy, excepting those of viii Preface the palpi of male spiders, were made by Mrs. Comstock; but most of the drawings were made by Miss Anna C. Stryke. The chapter on the external anatomy of spiders was prepared primarily to explain the terms used in the following pages; but it is hoped that it will also help to bring about a greater uni- formity in the terms employed by writers on the Arachnida than exists at present. I lay aside this work, which has occupied all the time that could be spared from my other duties for more than a decade, with the hope that it will serve to render easier the entrance into a field of study that is filled with interest and the hope that it may stimulate others to carry on the study much farther than 1 have been able to do. John Henry Comstock. Entomological Laboratory, Cornell University, March, 191 1. IX CONTENTS CHAPTER PACE Introduction xiii I. Spiders and Their Relatives 3 1. The zoological position of the Arachnida . . 3 11. The characters of the Arachnida .... 9 in. The orders of the Arachnida 12 II. The External Characters of Spiders .... 95 The external anatomy of spiders .... 95 III. The Internal Anatomy of Spiders 137 IV. The Life of Spiders 177 1. Methods of study 177 11. The development of spiders 182 in. The food of spiders 185 iv. Means by which spiders obtain their prey . 186 v. The silk of spiders 187 vi. The types of webs of spiders 193 vii. The building of an orb web 196 viii. The nests of spiders 206 ix. The pairing of spiders 207 x. The motherhood of spiders 208 xi. The venom of spiders 213 xii. The aeronautic spiders 21 i V. The Order Araneida or Spiders 218 VI. The Superfamily Avicularioidea or Tarantulas 22X VII. The Superfamily Argiopcidea or True Spiders . 2^7 XI INTRODUCTION Of all of our little neighbours of the fields there are none that are more universally shunned and feared than spiders, and few that deserve it less. There is a widespread belief that spiders are dangerous, that they are liable to bite, and that their bites are very venomous. Now this may be true of certain large species that live in hot countries; but the spiders of the temperate regions are practically harmless. It is true, spiders bite and inject venom sufficient to kill an insect into the wounds made by their fangs. But they are exceedingly shy creatures, fearing man more than they are to be feared. If an observer will refrain from picking up a spider there is not the slightest danger of being bitten by one; and, excepting perhaps a single uncommon species, no spider is known in the northern United States whose bite would seriously affect a human being. On the other hand, spiders are exceedingly interesting sub- jects for study; for some of the most remarkable exhibitions of instinctive powers are presented by them. What product of instinctive skill is more wonderful than the web of an orb-weaving spider! 1 le who loves the out-of-doors will find the interest incident to his walks greatly increased if he learns something of the habits of spiders. Their webs are to be found everywhere; and those of the different species differ greatly in structure, varying from an irregular, tangled maze, as that of the common domestic spider, to the wonderfully symmetrical nets of the garden-spiders. If spiders did not occur in our fauna, and if the keepers of a zoological garden were to bring from some remote part of the world living examples of the little animals that spin from their bodies threads of silk of different kinds, some dry and in- elastic, some viscid and elastic, and some, as the hackled band of Filistata, of wonderful complexity of structure, and with these threads construct snares of surprising regularity for trapping their prey, the presence of such marvellous animals would at- Introduction tract general attention, and we would make long journeys to see them. Fortunately, however, this marvel can be seen at home by any one that has eyes and will look. While the web-building spiders are those that most often attract attention, there are many that differ greatly from these in habits; and the stratagems employed by these to escape their enemies and to obtain their prey, in many cases, are scarcely less wonderful than those of the web-building species. In a word, the abundance of spiders, the great variations in the habits of the different species, and the high development of instinctive powers of many of them, render them exceedingly available for purposes of study of animal behaviour, whether this study be pur- sued by the lover of nature for his own enjoyment or by the teacher who wishes to use it as a means of interesting young people in the world about us and in training their powers of observation. The structure of spiders also offers attractive fields for study. This is especially true if attention be given to the correlation of structure and habits. As we find here the most elaborate spinning habits, so too we find here the most complicated organs for the production and manipulation of the silk which is spun. Some spiders are sedentary, either trapping their prey by snares or lying in ambush for it; others, like wolves, stalk their prey; some make use of any retreat that they find; while others dig tunnels in the earth; of the burrowing species, some merely strengthen the walls of their burrow with silk, leaving the entrance a simple opening into the earth; some build a watch-tower or turret about the entrance; and some close the entrance with a cunningly constructed hinged door. In each case the structure of the spider is specialized in a way that adapts it to its peculiar mode of life. Many of these correlations can be readily seen by the com- paratively untrained observer. The short and stout legs of the jumping spiders, the longer and more slender legs of the running species, the extra claw on each foot of those that cling to webs, the rakes of the chelicerae or jaws of the burrowing tarantulas, the pearly lustre of the "night-eyes" of those that live in dark places, and the protective colours of many species are all easily observed adaptations to peculiar modes of life. And for the trained observers many problems in the morphology of these animals await solution. xiv Introduction While the chief object of this book is to furnish an intro- duction to the study of the structure, classification, and habits of spiders, it has seemed wise to include in it accounts of the near relatives of spiders, of the other orders of the class Arachnida to which the spiders belong. Some of these, as the harvestmen, the mites, and the pseudoscorpions, are common in all parts of our country, and will be observed by all students of spiders. Others, as the scorpions and the whip-scorpions, abound in the warmer parts of our country and will be found by those who study there or who receive collections from the South. As no general work treating of the North American representatives of all of the orders of the Arachnida has been published, it is believed that the account of them given here will be a welcome addition to "The Spider Book." THE SPIDER BOOK CHAPTER I: SPIDERS AND THEIR NEAR RELATIVES Class Arachnida I.— THE ZOOLOGICAL POSITION OF THE ARACHNIDA Spiders, scorpions, harvestmen, mites, and certain other less familiar forms constitute a group of animals which is known to zoologists as the Class Arachnida (A-rach'ni-da). This is one of several classes of animals that agree in having the body composed of a series of more or less similar rings or segments, and in having some of these segments furnished with jointed legs (Fig. i). All the animals possessing these characteristics are classed together as the Arthropoda (Ar-throp'o-da), which is one of the chief divisions or phyla of the animal kingdom. A similar segmented form of body is found among worms; but these are distinguished from the arthropods by the absence of legs. It should be re- membered that many animals com- monly called worms, as the tomato- worm, apple-worm, etc., are not true worms, but are the larvae of insects, and have legs (Fig. 2); the angle-worm is the most familiar example of a true worm. The Phylum Arthropoda is the largest of the phyla of the animal king- dom, including many more species than all the other phyla taken together. The more familiar of the classes included in it are the six mentioned below. Besides these there are other classes, FiK. 1. A SCORPION. ONE OF THE ARTHROPODA Spiders and Their Near Relatives represented by less familiar animals, which also have the body segmented and possess jointed legs. For an account of the classes of arthropods not mentioned here, and for discussions of the relations of the classes of arthropods to each other, the reader is referred to more general works on zoology. I. Class Crustacea (Crus-ta'ce-a). — The more familiar representatives of the Crustacea are the cray-fishes, the lobsters, the shrimps, and the crabs. Cray-fishes (Fig. 3) abound in our brooks, and are often improperly called crabs. The lobsters, the shrimps, and the true crabs live in the sea. The Crustacea are essentially aquatic animals; a few of them live in damp places on land, but most of them live in the water. They breathe either through the general surface of the body or by means of gills; they are never furnished with tracheae as are nearly all other arthropods. The Crustacea differ also from all other arthropods in having two pairs of antennas. In many of them the head and the thorax, the part of the body which bears the ambulatory legs, are united, forming a region known as the cephalothorax; the region behind the cephalothorax is the abdomen. The examples named above are among the more conspicuous members of the class; but many other smaller forms abound both in the sea and in fresh water. Some of the more minute fresh-water forms are almost sure to occur in any fresh-water aquarium. In Fig. 4 are represented three of these, greatly enlarged. Among the Crustacea that live in damp places on land are the sow-bugs, Oniscidcc (O-nis'ci-dae). These frequently occur about water-soaked wood. One of them is represented in Fig. 5. On the sea-coasts an immense number of species of Crustacea occur. II. Class Diplopoda (Di-plop'o-da). — This class includes the millipedes. These are air-breathing arthropods in which the head is distinct, and the remaining segments of the body form a continuous region (Fig. 6). The most striking char- acteristic is the fact that most of the body-segments bear each two pairs of legs. As a rule, the body is not flattened as with the centipedes, and the antennae are comparatively short and few- jointed. The millipedes live in damp places and feed on decaying htj Hk> Fig. 2. THE " CARAWAY-WORM," THE LARVA OF A BUTTERFLY Fig. 3. A CRAY-FISH Fig. 5. A SOW-BUG (Cylisticus con- vexus) (after Sars) Fig. 4. CRUSTACEA a, Cypridopsis b, Cyclops c, Daphnia Fig. 6. A MILLIPEDE 5 Spiders and Their Near Relatives vegetable matter. They are harmless, except that occasionally they feed on growing plants. III. Class Chilopoda (Chi-lop'o-da). — The Chilopoda in- cludes the centipedes. These, like the millipedes, are air-breathing and have an elongated body composed of similar segments (Fig. 7). They can be distinguished from the millipedes by the fact that each segment bears only a single pair of legs. The body is usually flat- tened, and the antenna? are usually long and many-jointed. . The centipedes are predaceous, feed- ing on insects; they are common under stones and other objects lying on the ground. Many species are venomous. The poison glands open through the claws of the first pair of legs, which are bent forward so as to act with the mouth-parts. These creatures abound in all parts of the United States; those that are found in the North are comparatively small, and Fig. 7. a centipede rarely, if ever, inflict serious injury to man; but the larger species, which occur in warmer regions, are said to be extremely venomous. Formerly the millipedes and the centipedes were grouped together as the Class Myriapoda (Myr-i-ap'o-da); and this grouping is retained in many recent zoologies. IV. Class Hexapoda (Hex-ap'o-da). — The class Hexapoda comprises the various orders of insects. The members of this class are air-breathing arthropods, with distinct head, thorax, and abdomen. They have one pair of antennas, three pairs of legs, and usually one or two pairs of wings in the adult state (Fig. 8). Among the more familiar examples of insects are grass- hoppers, dragon-flies, butterflies, moths, and beetles. There are so many excellent popular works treating 6 Fig. 8. AN INSECT; A WASP, WITH THE HEAD, THORAX AND ABDO- MEN SEPARATED /, thorax a, abdomen Spiders and Their Near Relatives of insects that it is not necessary to dwell on this class here. V. Class Pal^eostracha (Pa-lae-os'tra-cha). — This class is composed almost entirely of extinct forms, there being living representatives of only a single order, the Xipbosura (Xiph-os-u'ra). And this order is nearly extinct; for of it there remains only the genus Limulus (Lim'u-lus), represented by only five known species. The members of this genus are known as king-crabs or horseshoe-crabs; the former name is suggested by the great size of some of the species, the latter, by the shape of the cephalothorax (Fig. 9). The king-crabs are marine; they are found on our Atlantic Coast from Maine to Florida, in the West Indies, and on the eastern shores of Asia. They are found in from two to six fathoms of water on sandy and muddy shores; they burrow a short distance in the sand or mud and feed chiefly on worms. The single species of our coast is Limulus polyphenols. In Limulus the body-segments are grouped in two regions, cephalo- thorax and abdomen ; the abdomen is terminated by a long, strong spine. The cephalothorax bears six pairs of appendages; these correspond to the six pairs of append- ages of Arachnida described later; and, as in the Arachhida, none of the appendages are jaw-like. The food is crushed by the basal part of the leg-like appendages, which are situated round the mouth. The abdomen also bears six pairs of append- ages; these are plate-like and the members of each pair are united at the base. The first pair of abdominal appendages form a nearly semi- circular plate, which nearly covers the following appendages. On the posterior side of this plate are two openings, the outlets of the reproductive organs. Each of the following pairs of append- Fig. 9. A HORSESHOE-CRAB (Limulus) (after Leuckart) Spiders and Their Near Relatives ages bears a pair of gills. These are termed book-gills, each being composed of many thin plates, like the leaves of a book. In its more general characteristics, Limulus is closely allied to the Arachnida, except that its respiration is aquatic. So close is this resemblance in structure to the Arachnida that many zoologists, and among them some of those who have studied Limulus most carefully, regard the Xiphosura as an order of the Arachnida. A more conservative view is to regard the Palaeostracha and the Arachnida as two closely allied but dis- tinct classes. The most familiar of the fossil representatives of the Palae- ostracha are the Trilobites. VI. Class Arachnida (A-rach'ni-da). — The members of this class are air-breathing arthropods, in which the head and thorax are usually grown together, forming a cephalothorax, which have four pairs of legs, and which apparently have no antennas. The characteristics of the Arachnida are more fully discussed in the next section of this chapter. TABLE OF CLASSES OF ARTHROPODS The more striking of the distinguishing characters of the six classes of arthropods mentioned above can be stated in a tabular form as follows: A. With two pairs of antennae and at least five pairs of legs; respiration aquatic. Crustacea AA. With one pair of antennae or apparently with none; respira- tion, except in Limulus, aerial. The number of legs varies from six to many. With one pair of feeler-like antennae. C. With more than three pairs of legs, and without wings. D. With two pairs of legs on some of the body-segments. Diplopoda DD. With only one pair of legs on each segment. Chilopoda CC. With only three pairs of legs, and usually with wings in the adult state. Hexapoda BB. Apparently without antennae. C. Respiration aquatic. Pal^ostracha CC. Respiration aerial. Arachnida 8 Spiders and Their Near Relatives II —THE CHARACTERS OF THE ARACHNIDA At first sight, the Arachnida appear to be distinguished from all other air-breathing arthropods by the absence of antennae; for they have no feelers projecting forward from the head. But it has been found that a pair of nippers, the chelicera?, with which the head is armed, correspond to the second antennas of Crustacea. Vestiges of the first antennae have been observed in the embryos of certain arachnids; but these appendages either disappear completely before birth or, according to the views of some writers, become consolidated to form the upper lip or rostrum. We can say, therefore, that in the Arachnida the first pair of antennae are wanting as distinct appendages, and the second antennae are modified so as to form prehensile organs. Most Arachnida differ from all other air-breathing arthropods in having the segments of which the head and thorax are composed consolidated so as to form a single region, the cephalothorax ; but in certain generalized forms the thoracic segments are more or less distinct. In most cases the cephalothorax and abdomen are distinct; but in the mites the entire body forms a single region. In the scorpions and in some other forms the abdomen i, divided into two portions; a broad preabdomen, and a slenderer tail-like division, the postabdomen. Perhaps the most distinctive characteristic of the Arachnida is the fact that in this class the combined head and thorax bears only six pairs of appendages; this, however, is also true of the Palaeostracha, which some writers class with the Arachnida. The nearest approach to this condition among air-breathim* arthropods is found in the insects, where the head and thorax bear seven pairs of appendages. Another striking characteristic of the Arachnida, which, however, is also possessed by the Palaeostracha, is the absence of true jaws. In other arthropods one or more pairs of append- ages are jaw-like in form and are used exclusively as jaws; but in the Arachnida the prey is crushed either by the prehensile antennae alone (as in Kanenia) or by these organs and other more or less leg-like appendages. The arachnids suck the blood of their victims by means of a sucking stomach; they crush 0 Spiders and Their Near Relatives their prey, but do not masticate it so as to swallow the solid parts.* The Arachnida are air-breathing. Two forms of respira- tory organs exist in this class: first, the book-lungs; and second, the tracheae. Both of these are described in the chapter on the internal anatomy of spiders. In the mode of respiration, the Arachnida differ from the Palaeostracha, with which they agree in the number of cephalothoracic appendages and in the absence of true jaws. The reproductive organs open near the base of the abdomen, on the ventral side. In this respect the Arachnida resemble Limulus, the millipedes, and the Crustacea, and differ from the centipedes and insects, in which the reproductive organs open near the caudal end of the body. The eyes are simple, that is, each eye is covered with a single cornea, not facetted like the compound eyes of insects. The number varies from two to twelve, and some species are eyeless. The eyes vary greatly in their position. In some forms (Avicularioidea) they are borne on an ocular tubercle near the middle of the head. In this case there are two large round median eyes, one on each side of the median line; on each side of the median eyes, on the base of the tubercle, are three lateral eyes, which differ in size, shape, and appearance, both from the median eyes and from one another. This is probably the primi- tive arrangement of the eyes; but in most forms, the lateral eyes have wandered off laterally on to the cephalic lobes, which con- stitute the lateral portions of the head, and the optic tubercle is obliterated (Bernard '96). f A similar migration of the paired ocelli of insects has been pointed out by the writer (Comstock and Kochi '02). In some of the more generalized insects, the three ocelli are borne by the front; but in most insects they have wandered off from this sclerite into the epicranial suture or even on to the vertex, which is developed from the cephalic lobes of the embryo. Of the six pairs of appendages borne by the cephalothorax, in most forms, the first two pairs are used for seizing and crushing •For possible exceptions to this see accounts of the habits of the Solpugida and of the Phalan- gida, in the next chapter. tThc complete titles of works referred to in parentheses in the text a(e given in the bibliog- raphy at the end of the volume. IO Spiders and Their Near Relatives prey, and the last four, as legs; but there is considerable lack of uniformity in this respect. Owing to this lack of uniformity in the function of some of the appendages in different orders some writers designate the six pairs of appendages by numbers; but the older authors gave special names to the first and second pairs, and termed the last four pairs legs. The older nomen- clature is so well established that it does not seem wise to attempt to change it, notwithstanding that in one order the second pair of appendages function as legs, and in another order, the third pair of appendages function as feelers. The first pair of appendages are termed the chelicerce (che- Iic'e-rae). They are situated in front of the mouth; all other appendages are postoral, except perhaps the second pair. The second pair of appendages are the pedipalps (ped'i- palps). These are situated immediately behind the mouth, or one at each side of it. They are always more or less leg-like in form; and in the Microthelyphonida they function as legs. Following the pedipalps are the four pairs of legs. In the Pcdipalpida, the first pair of legs function as feelers. Usually the basal parts of the pedipalps bear masticatory Fig. 10. TARSAL CLAWS OF A SPIDER Fig. it. A CHELA oi \ PEDIPALPOF A SCORPION ridges for crushing the prey. Sometimes the crushing organ is a distinct sclerite borne by the basal segment of the pedi- palp; it is then known as an endite. Masticatory ridges or endites are sometimes borne by the first or the first and second pairs of legs. The last segment of an appendage may bear claws, which resemble more or less the tarsal claws of insects. (Fig. 10.) In other cases the last segment itself is claw-like; in this case a pincer- - i Spiders and Their Near Relatives like organ is formed. Two types of pincers exist in the Arach- nida. The first is known as a chela; an illustration of this is a great claw of scorpions. A chela is formed by the next to the last segment of an appendage being prolonged on one side so as to oppose the last segment (Fig. n). An appendage bearing a chela is said to be chelate. In descriptions of chelate claws, the last segment is termed the movable claw of the chela; and the prolongation of the next to the last segment opposed to this, the fixed claw of the chela. Another type of pincers is produced when the last segment of an appendage is claw-like and is folded back into a groove in the next to the last segment, like the blade of a pocket-knife into the handle (Fig. 12). An append- age bearing a pincer of this type may be said to be uncate. These two types of pincers are not distinct, intermediate forms being present. Such intermediate forms may be termed semichelate; the pedipalps of Mastigoproctus are illustrationsofthesemichelatetype. A detailed account of the structure of spiders is given in the following chapters; it is not necessary, therefore, to discuss further the anatomy of arachnids in this place. III.— THE ORDERS OF THE ARACHNIDA According to the classification that is most generally accepted, the class Arachnida is divided into nine orders. One of these orders, the Ricinulei, is not represented in North America, and, therefore is not discussed here. The eight orders included in our fauna can be separated by the following table. TABLE OF THE ORDERS OF THE ARACHNIDA A. Abdomen distinctly segmented. B. Abdomen with a tail-like prolongation. Fig. 12. AN UNCATE CHELICERA 12 Spiders and Their Near Relatives C. Tail stout and armed with a sting at the end; first pair of legs not greatly elongated; a pair of comb-like ap- pendages on the lower side of the second abdominal segment in the adult. (Scorpions) P. 21. Scorpionida CC. Tail slender, usually whiplash-like, without a sting; first pair of legs much longer than the others; without comb-like appendages on the abdomen. D. Body of minute size being less than one tenth inch in length (Micro-whip-scorpions) P. 13. MlCROTHELYPHONIDA DD. Body of moderate or large size. (Whip-scorpions). P. 16. Pedipalpida BB. Abdomen without a tail-like prolongation. C. Palpi with pincer-like claws. (Pseudoscorpions) P. 39. PSEUDOSCORPIONIDA CC. Palpi without pincer-like claws. D. Abdomen joined to the thorax by a slender stalk; front legs greatly elongated and with whiplash-like tarsi. (Whip-scorpions) P. 16. Pedipalpida DD. Abdomen broadly joined to the thorax. E. Legs usually very long and slender; thorax not distinctly divided into three segments. (Har- vestmen) P. 53. Phalangida EE. Legs moderately long; head distinct from thorax; thorax distinctly divided into three segments. P. 32. Solpugida AA. Abdomen unsegmented. B. Abdomen joined to the cephalothorax by a short, narrow stalk. (Spiders) P. 39. Araneida BB. Abdomen fused with the cephalothorax. (Mites) P. 8. ACARINA Order MlCROTHELYPHONIDA* The Micro-Whip-scorpions The tiny creatures constituting the order Microthelvphonida (Mi-cro-thel-y-phon'i-da) bear striking resemblance in the form This order was established under the above name by Grassi ('86). Later Thorell changed th.' name to Palpigradi; but this latter name cannot be justly accepted, although it is shorter and equallyappropriate- 13 Spiders and Their Near Relatives of the body to members of the Thelyphonidae (p. 18); it was this that suggested the name of the order. They differ greatly from the whip-scorpions, however, both in size and in structure; the larger of the species found, as yet, measure less than one tenth of an inch in length, including the tail-like appendage. The form of the body and the more general features of the appendages are shown in Fig. 13. The thorax appears to consist of only two segments when seen from above, the tergum of the segment bearing the fourth pair of appendages being a part of the carapace. On the ventral aspect of the cephalothorax there are four sternites; a larger one corresponding to the pedipalps and the first pair of legs, and three smaller ones corresponding to the second, third, and fourth pairs of legs respectively. The abdomen is distinctly segmented, and is terminated by a slender appendage con- sisting of about fifteen segments. Eyes are wanting. The mouth is a mere slit in an oral prominence, which is situated far forward so that it is partly between the bases of the chelicerse; in other words, the mouth has not migrated so far back as in other arachnids. None of the appendages are furnished with either masticatory ridges or endites. This is the simplest oral apparatus found in the arach- nida. The chelicerae are chelate, and are the only chelate append- ages. The pedipalps are leg-like and are terminated by a pair of claws, as are the legs; or to express it differently, the pedipalps have not been modified into organs for some other function than locomotion, as is the case with the more specialized arachnids. It would be correct, therefore, to say that these creatures possess five pairs of legs; but to avoid confusion it is better to restrict the term legs to the last four pairs, as is done in describing other arachnids. Each pedipalp consists of nine segments. Fig. 13. K(EN- ENIA WHEE- LERI (after Wheeler) 14 Spiders and Their Near Relatives The first pair of legs, using the term in the restricted sense just indicated, are the longest of the appendages, and resemble the corresponding appendages of the whip-scorpions in having the tarsi broken up into several segments, each of these legs consisting of twelve segments. The second and third pairs of legs are seven-jointed; the fourth, eight-jointed. The respiratory organs, according to the investigation of Miss Rucker foi), consist of three pairs of lung-sacs, which are situated in segments four, five and six of the abdomen, with their corresponding orifices on the ventral surface. These sacs are evidently evaginated through the internal blood-pressure, and invaginated by dorso-ventral muscles, a pair for each pair of sacs. When invaginated, the sacs appear like diminutive tracheae if stretched by the retractor muscles; but if the latter become relaxed, allowing the sac to flatten dorso-ventrally and wrinkle, they appear like diminutive book-lungs. The external reproductive organs are quite complicated; they are borne by the second and third abdominal segments. It should be borne in mind that this somewhat detailed characterization of the Microthelyphonida is based upon the single known genus of the order; and that the discovery of other genera may necessitate some modifications of it. Family KCENENIIDiE (Kcen-e-ni'i-dae) As yet only representatives of a single genus, Kanenia (Koe-ne'ni-a) belonging to this order have been found. This is represented in Texas by two species, which will doubtless be found in other parts of the South; and probably other species will also be discovered. The genus is widely distributed, species having been found in Italy, Bay of Siam, Chili, and Paraguay, as well as in this country. Kanenia lives under stones in company with insects of the order Thysanura. The species are of a translucent white colour except the blades of the chelicerae, which have the yellow tint of thickened chitin. Excellent accounts of our species, Kanenia wheeleri and Kanenia jlorencia, are given by Wheeler ('oo) and Rucker ('01 and '03). 15 Spiders and Their Near Relatives Order PEDIPALPIDA* The Whip-scorpions These strange creatures are found in our country only in the extreme southern part, they being tropical animals; but they are distributed from the Atlantic to the Pacific. In their general form they bear some resemblance to scorpions; but they can be easily distinguished from scorpions by the form of the pedipalps, of the first pair of legs, and of the postabdomen. The common name whip-scorpions was doubtless suggested by the slender caudal appen- dage of the Thelyphonidae (Fig. 14); but it is almost as appropriate for the forms that lack this appendage, as they have the tarsi of the front legs broken up into many small segments, which gives this part of the leg a whiplash-like appearance (Fig. .8). These arachnids are of moderate or large size, none of them being minute like the Microthely- phonida. The abdomen is segment- ed, and distinctly separate from the thorax. In one family the carapace is divided by transverse sutures; in the other two families it is not so divided. The chelicerae are two- jointed and uncate; that is the second segment is claw-like and folds back upon the end of the first segment. A remarkable feature, in some members of the order if not all, is that the chelic- erae are attached to the head by a thin membrane in such a way as to be capable of being retracted into the head for a considerable distance (Laurie '94). The pedipalps are very stout and are six- jointed; they present the three types of claws, one in each of the * The original form of this name was Pedipalpi, a family name proposed by Latreille (1806); and this forji is still r.-tained by many writers even though they rank the group as an order. 16 Fig. 14. MASTIGO- PROCTUS GIGANTEUS Spiders and Their Near Relatives three families. The first pair of legs are elongated and are modified into feelers, the tarsus being divided into many seg- ments, the last of which has a rounded tip instead of claws. The ambulatory organs are therefore reduced to three pairs. The respiratory organs are book-lungs; there are two pairs of these; they open on the posterior edge of the second and of the third abdominal segments. Among the more important recent general works on this order is that of Kraepelin ('99) which treats of the classification of the order and that of Borner ('04), which is anatomical. The order includes three families, each of which is represented in the United States; the families can be separated as follows: A. Cephalothorax longer than broad with nearly parallel lateral margins. B. l7- BB AA. Carapace divided by a transverse suture which separates off the part of the thorax bearing the third and fourth pairs of legs; the caudal appendage consists of a single segment, with or without a knob at the end. P Shizonotid^e Carapace not divided by a transverse suture; the caudal appendage long and many-jointed. P. 18. Thelyphonid/e Cephalothorax broader than long, with the lateral margin strongly arched. P. 19. Tarantulid/e Family SHIZONOTID^E (Shiz-o-not'i-dae) Only a few representatives of this family are known; but they are regarded with great interest on account of the generalized condition of the carapace, in which some of the transverse sutures are retained (Fig. 15). The eyes are wanting. Certain light-coloured areas of the cuticula have been mistaken for vestiges of lateral eyes; but Borner ('04) states that there is no modification of the hypodermis below these areas. The caudal appendage is short, either unsegmented or, in certain exotic forms, with a knob-like seg- ment at the end. FiK. is. TRITHY- RFl/S CAMBRTDGEI (after Borner) ■7 Spiders and Their Near Relatives A single species belonging to this family has been found in the United States; this is Tritbyreus pentapeltis (Tri-thyr'e-us pen-ta-pel'tis), which occurs in the desert regions of southern California. Only a few specimens have Q^-~--x been taken; the largest of these meas- f \ ured less than one half inch in length. Figure 16 represents some of the details of structure of this species as given by Cook ('99). Family THELYPHONIDAEfThel- y-phon'i-dae) This family includes the tailed whip-scorpions, those in which the caudal end of the abdomen is furnished with a slender, many-jointed appendage (Fig. 14). In this family the carapace is not divided by transverse sutures. Eight eyes are present, two, the median eyes, near the centre of the front part of the head, and a group of three, the lateral eyes, on each side farther back. The pedipalps are stout and armed with tooth-like proc- esses (Fig. 17). They are semichelate, the projecting process of the fifth seg- ment being much smaller than the sixth segment which forms the other part of the chela; in the ordinary chelate type the opposite of this is the case. These pedipalps are remarkably developed for crushing the prey; they might be de- scribed as plurichelate; for in addition to the pincers formed by the fifth and sixth segments, another pair is formed by the fourth and fifth; and the second segment bears a prominent semicircular process, armed with strong teeth, which can be opposed to the third and fourth segments. The chief use of this process of the second seg- ment is to be opposed to the corresponding process of the other 18 Fig. 16. TRITHYREUS PEN- TAPELTIS (after Cook), o, body without appendages; b, carapace more enlarged; c, caudal segments lateral view Fig. 17. THE PALPUS OF MASTIGOPROCTUS Spiders and Their Near Relatives pedipalp. The first segments of the pedipalps meet on the middle line on the ventral side of the head. The flexible tip i f the first legs is composed of nine segments; and each of the six ambulatory legs is furnished with two tarsal claws. This family is represented in the United States by onlv a single species, the giant whip-scorpion, Mastigoprodus giganteus (Mas-ti-go-proc'tus gi-gan-te'us). This species measures when full-grown from four to five inches in length. Figure 14 represents one less than natural size. In some parts of the South they bear the local name grampus, and are greatly feared on account of their supposed venomous powers; but it is probable that there is no foundation for this fear; for although it has been stated often that their bites are poisonous, 1 can find no direct evidence that this is true, and no poison glands have been found in this order. This species burrows in sand under logs or other objects lying on the ground; it doubtless feeds on any insects that it can capture. Family TARANTULIDiE (Tar-an-tu'li-dae) This family includes the tailless whip-scorpions. These resemble the tailed whip-scorpions in the consolidated condition Fig. 18. TARANTULA MARGINEMACULATA of the carapace and in the possession of eight eyes. They differ in the absence of the caudal appendage and in having the abdomen joined to the thorax by a slender pedicel. The flexible tip of the first legs is very long and is composed of very many segments (Fig. 18). This family is the Phrynidae of some authors; it is represented 19 Spiders and Their Near Relatives in the United States by two genera, Acanthophrynus and Tarantula. These are separated as follows: A. Front border of the cephalothorax armed with long teeth; next to the last segment of the pedipalp with only one long spine on the upper inner margin. P. 20. Acanthophrynus AA. Front border of the cephalothorax unarmed or only dentic- ulate; next to the last segment of the pedipalp with at least two long spines on the upper inner margin. P. 20. Tarantula The genus Acanthophrynus includes only a single known species, Acanthophrynus coronatus (A-can-tho-phry'nus cor-o- na'tus); this is found in California and Mexico. This species is larger than those of the following genus, attaining a length of nearly two inches. The genus Tarantula (Ta-ran'tu-la) is represented in the United States by three species. We have here an unfortunate instance in which the technical and popular uses of a name are very different. For although, according to the law of priority the generic name Tarantula must be applied to these animals, the popular name tarantula is irrevocably applied, in this country at least, to the large four-lunged spiders of the South and the Southwest. Four species of Tarantula are known; these are separated by Kraepelin as follows: A. With two short spines between the longest spines of the tibia of the pedipalps. T. fusimana AA. With only one short spine between the longest spines of the tibia of the pedipalps. B. The intermediate spine between the two principal spines of the pedipalps considerably longer than the spine immediately preceding the first of the two principal spines. T. whitei BB. The intermediate spine shorter than the one preceding the first of the principal spines. C. The principal spine on the upper edge of the next to the last segment of the pedipalps preceded by a dis- tinct spine (Fig. 19). T. palmata 20 Spider and Their Near Relatives CC. The above-mentioned spine preceded by a short tu- bercle (Fig. 20). T. marginemaculata Of these species Tarantula palmata alone has not been found in the United States. 1 found T. marginemaculaia (Fig. 18) not uncommon near Miama, Fla., under logs. It is a very active creature. According to several observers, the eggs of members of this genus are carried in a sac formed of a dark brown transparent material, Flg' I9 containing some threads, and attached to the ventral surface of the abdomen (Laurie '94). It is supposed that the substance of which the egg-sac is composed exudes from openings in the first abdominal segment (Bernard '95); but our knowledge of the spinning glands of these animals is very in- complete. Order SCORPIONIDA The Scorpions The order Scorpionida (Scor-pi-on'i-da) includes only the scorpions. Although these creatures do not live in the North, they have been pictured so often that their form is well-known. Their most striking features are the large size of the pedipalps which are furnished with very stout chelae, and the division of the abdomen into two portions: a broad preabdomen, consisting of seven segments; and a slenderer tail-like division, the post-abdomen or cauda, con- sisting of five segments. At the end of the postabdomen there is a large poison-sting, which appears like a segment (Fig. 21). The cephalothorax is compact and unsegmented; the abdomen is broadly joined to the thorax; the chelicerae are chelate; the coxae of the pedipalps are fitted for crushing the prey, which is seized by the large chelae; the remaining four pairs of cephalothoracic appendages are fitted for .: 1 Fig. 21. A SCORPION Spiders and Their Near Relatives walking; they are seven-jointed, the tarsus consisting of three segments, and the patella being wanting; the legs are not chelate, but are furnished with tarsal claws. The coxae of the first two pairs of ambulatory legs bear each an endite, which is directed toward the mouth, and doubtless helps hold the prey opposite the mouth (Fig. 22). The cephalothorax bears a pair of eyes near the middle line, the median eyes, and on each side near the cepha.lo-lateral margin a group of from two to five, the lateral eyes. A few scorpions are blind. Full-grown,, scorpions possess a pair of comb-like organs, the pectines (pec'ti-nes), on the lower side of the second abdominal segment (Fig. 22). The function of these organs is not yet known, but it has been suggested that it is tactile. " Pocock noticed that a scorpion which had walked over a portion of a cockroach far enough for the pectines to come in contact with it immediately backed and ate it." Scorpions breathe by means of book-lungs, of which there are four pairs, opening on the lower side of the third to the sixth abdominal segments. The sexes of scorpions differ in that the male has broader pincers and a longer postabdomen. Scorpions do not lay eggs, the young being developed within the mother; after the birth of the young, the mother carries them about with her for some time, attached by their pincers to all portions of her body. Scorpions live in warm countries. They are common in the southern portion of the United States, but are not found in the North. They are nocturnal, remaining concealed during the day, but leaving their hiding places at dusk. When they run, the pedipalps are carried horizontally in front, and are used partly as feelers and partly as raptorial organs; and the postabdomen is bent upward over the back by some, others Fig. 22. VENTRAL ASPECT OF THE CEPHALOTHORAX AND TWO. THE THIRD AND FOURrH, AB- DOMINAL SEGMENTS OF CEN- TRURUS GRACILIS ~> ~) Spiders and Their Near Relatives Fig. 23. CARAPACE OF A SCORPION drag it along behind. They feed upon spiders and large insects, which they seize with the large chelae of their pedipalps, and sting to death with their caudal poison-sting. Scorpions are shy animals; when disturbed they attempt to run away and hide and do not sting unless molested. The sting of a scorpion rarely if ever proves fatal to man, although the larger species, which occur in the Tropics, produce serious wounds. It is said that the best remedy for the sting of a scorpion is ammonia applied externally, and also administered in small doses internally. Scorpions attain maturity slowly, Fabre (07) who studied them in con- finement, came to the conclusion that it required five years for them to reach their full size. In the classification of scorpions the following special terms are used: Upon the carapace, the dorsal covering of the cephalothorax, ihere are often more or less distinct keels; these are distinguished as the fore, middle, and hind, median and lateral keels respectively; these keels are connected with each other in various ways (Fig. 23). That part of the fore median keel which is above a median eye is termed the superciliary ridge. Upon the postabdomen, or cauda, there are often two pairs of keels upon the dorsal aspect and two pairs on the ventral aspect of some or of all of the segments. The two pairs of keels nearest the middle line of the body are designated as the dorsal median keels and the ventral median keels respectively. Outside of these are the dorsal lateral keels and the ventral lateral keels. In Fig. 24. the addition to these eight principal keels accessory CHELA OF A , , , scorpion "ee's ma>' be present. ff, fixed finger ] he large basal portion of the chela of a mj. movable finger pedipalp fc termed fa /W (Fjg ^ . and the apposed portions are distinguished as the fixed finger and the movable finger respectively, the movable finger being the last segment of the pedipalp. 23 Fig. 25. A COMB OF A SCORPION Fig. 26. TARSUS OF BUTHUS Spiders and Their Near Relatives The sclerite on the middle line of the body from which the combs arise is termed the basal piece of the combs (Fig. 25); the series of sclerites that form the front margin of a comb con- stitute the marginal area; next to these there is a series of sclerites constituting the middle area; the small sclerites be- tween the middle area and the teeth are the fulcra; and the long slender appendages of the comb are the teeth. The characters presented by the tarsi of the legs, and especially of the last pair of legs, are much used, as, for example, the presence or absence of tarsal spurs and the number of these spurs when present. Sometimes the last segment of a tarsus is prolonged above the claws form- ing a dorsal lobe (Fig. 26); and sometimes this segment is pro- longed into a lobe on each side, the lateral lobes (Fig. 27) ; and there is often a more or less claw-like empodium below and between the claws (Fig. 26). About a score of species of scorpions are known to occur in the United States; besides these, other Mexican species may be found in southern Texas. A general work on the scorpions of the world was published by Kraepelin in 1899 and a synopsis of our species was published by Banks in 1900. The following account is based upon these two works and upon a study of the specimens in the collection of Cornell University. The most important work on the habits of scorpions is that of Fabre in the ninth series of his Souvenirs Entomologiques (1907). Kraepelin divides the order into six families; but only four of these families occur in the United States; these can be separated by the following table: TABLE OF FAMILIES OF SCORPIONS A. Only one spur at the base of the last tarsal segment of the last pair of legs, and this is on the outside. P. 28. SCORPIONID/E Fig. 27. TARSUS OF PANDINUS 24 Spiders and Their Near Relatives AA. One or two spurs on each side at the base of the last tarsal segment of the last pair of legs. . B. From three to five lateral eyes on each side. C. Sternum triangular (Fig. 22); usually a spine under the Sting. P. 25. BuTHIDyE CC. The lateral margins of the sternum nearly parallel (Fig. 34); sternum usually broader than long; no spine under the sting. P. 29. Ve|ovid/e BB. Only two lateral eyes on each side. P. 29. Chactid^e Family BUTHIDjE (Bu'thi-dae) The members of this family are most easily recognized by the form of the sternum, which is triangular in outline (Fig. 22). There are one or two spurs on each side at the base of the last tarsal segment of the last pair of legs. There are from three to five lateral eyes on each side. The hand of the chelae is rounded and the fingers are long. The last segment of the tarsus of the legs is not terminated by lateral lobes. There is usually a spine under the sting. This is a large family, containing more than 150 known species, representing 18 genera. Nearly one half of the species of scorpions occurring in our fauna belong to it. These represent four genera, which can be separated as follows: A. A distinct tarsal spur at the distal end of the first tarsal segment of the third and fourth legs (Subfamily Buthinae). P. 26. Uroplectes AA. No tarsal spur at the distal end of the first tarsal segment of the last pair of legs (Subfamily Centrurinae). B. The oblique rows of teeth on the edge of the fingers of the chelae have on each side a parallel row of minute teeth (Fig. 31). P. 27. Centrurus BB. The oblique rows of teeth on the edge of the finger of the chelae not accompanied by parallel rows of minute teeth. C. The ends of the oblique rows of teeth on the fingers of the chelae overlapping (Fig. 30). P. 27. Tityus CC. The ends of the oblique rows of teeth on the fingers of the chelae not overlapping but often connected in one direct line (Fig. 28). P. 26. Isometrus 25 Spiders and Their Near Relatives Genus UROPLECTES (U-ro-plec'tes) This genus is the only representative in our fauna of the sub- family Buthinae, which is characterized by the presence of a tarsal spur at the distal end of the first tarsal segment of the third and fourth legs. Of this genus the following species is the only one yet found within the limits of the United States. The Mexican Uroplectes, Uroplectes mexicanus (U. mex-i- ca'nus). — This is a pale species. There is no spine under the sting; the teeth on the finger of the palpus are in many oblique rows, with stouter teeth at the end of each and to one side; there are from thirty to thirty- five teeth in the combs; and the keels on the under side of the last caudal segment are very strongly toothed. This species has been found in Texas and in California. Genus ISOMETRUS (I-som'e-trus) In this genus, there are only a few oblique rows of teeth on the edge of the fingers of the chelae and these do not overlap (Fig. 28); there is a large spine under the sting (Fig. 29); and the abdomen has a single keel above. The following is our only species. The spotted Isometrus, Isometrus maculatus (I. mac-u-Ia'tus). — This is a dirty yellow species marbled and flecked with black. The body is thin and In the female the postabdomen is usually about as long as the rest of the body; in the male, it is often twice as long. The hand is long and thin, thinner than the tibia of the pedipalp; the finger is from one and a half to two times as long as the hand. The combs have from seventeen to nineteen teeth. to nearly two inches in length; the males, to nearly three inches. This species is distributed throughout the tropical and subtropical regions of the world; in this country it is found in southern Florida, and California, and, probably, in the inter- mediate regions. 26 Fig. 28. FINGER OF ISO- METRUS MACU- LATUS slender. Fig. 29. STING OF ISOMETRUS MACU- LATUS The female grows Spiders and Their Near Relatives Genus TITYUS (Tit'y-us) There are many overlapping oblique rows of teeth on the of the fingers of the chelae (Fig. 30). The following is the only species found in the United States. Tityus Jloridanus (T. flor-i-da'nus).— This is a dark, red-brown species measur- ing nearly three inches in length, found at Key West. The sting is long and curved; the tooth beneath it is acute, but short. i il Genus CENTRURUS (Cen-tru'rus) t Fig. 3°- Fig. 31- FINGER OF CENTRURUS The oblique rows of teeth on the edge of the fingers of the chelae have on each side a parallel row of minute teeth (Fig. 31). There is a tooth on the lower margin of the fixed finger of the chelicerae, fingerof and a spine under the sting may be either TITYUS .• present or wanting . Banks (00) lists seven species of this genus that are found in our fauna. He separates them as follows: A. No spine under the sting; postabdomen very long and slender. Occurs in California. Centrums exilicauda AA. At least a small spine or tubercle under the sting; post- abdomen less slender. B. Body striped with black and yellow. C. A small pale median spot on the anterior border of the cephalothorax, legs pale yellow, postabdomen pale. Occurs in the Southern States. Centrums caroliniauus No such median spot on the anterior margin of the cephalothorax, legs marbled with brown, postabdomen brown, dark stripes on the cephalothorax, broader than the preceding species. Occurs in Florida. Centrums hent{i Body nearly uniform reddish brown or blackish. Body a dark greenish black, cephalothorax very rough, postabdomen strongly granulate. Occurs in Texas. Centrums nigrescem 27 CC. BB. Spiders and Their Near Relatives CC. Body reddish or yellowish brown. D. Fingers paler than the .hand, yellowish, otherwise dark red-brown, spine under the sting often small and blunt. Occurs in Florida. Centrums margaritatus DD. Fingers usually darker than the hand. E. Colour yellowish brown, combs with rarely more than twenty-four teeth, spine under the sting not very prominent. Occurs in southern Florida. Centrums testaceus EE. Colour reddish brown, combs with usually more than twenty-five teeth, spine under sting well- developed, usually much larger than the preceding. Occurs in Florida. Centrurus gracilis Family SCORPIONIDiE (Scor-pi-on'i-dae) In this family there is only one spur at the base of the last tarsal segment of the last pair of legs and this is on the outside. The lateral margins of the sternum are nearly parallel. There are no spurs at the end of the first tarsal segment of the third and fourth legs. There are three lateral eyes on each side. The hand is usually flattened, seldom rounded, and there is rarely a spine under the sting. Two genera occur in our fauna. A. With a hump under the sting (Fig. 32). Diplocentrus AA. Without a hump under the sting. Opisthacanthus Genus DIPLOCENTRUS (Dip-lo-cen'trus) Two species belonging to this genus are found within the limits of the United States. Diplocentrus whitei (D. whi'te-i). — This is a Mexican species which is found in Texas and California. It can be distinguished from the following by the presence of from twelve to eighteen teeth in the comb. The full-grown male measures nearly or quite two inches in length. Diplocentrus lesueurii (D. le-su-eu'ri-i). — This species was described from Florida. It Fig. 32. sting of differs from the preceding in having only DIPLOCENTRUS r . . . . . , i whitei from six to eight teeth in the comb. 28 Spiders and Their Near Relatives Genus OPISTHACANTHUS (O-pis-tha-can'thus) Only one species of this genus occurs in our fauna. Opisthacantbus elatus (O. e-la'tus).- The cephalothorax is deeply emarginate on the anterior margin; the postabdomen is small; the chelae large. Comb with from four to fourteen teeth. The adult is sometimes three and one half inches in length. It is a West Indian species, which is found in southern Florida. Family CHACTIDiE (Chac'ti-dae) These scorpions can be distinguished from all others found in the United States by the presence of only two lateral eyes on each side. The family is represented in this country by a single genus. Genus BROTEAS (Bro'te-as) In this genus, the last segment of the tarsus bears two rows of bristles on the under side (Fig. 33). Only one species has been found in the United States. Broteas alleni (B. al'le-ni).-- This is a small species, the length of the body and tail together of the female being but little more than one inch and of the male, Fig. 33- about one and one half inch. The dorsum is beauti- J^/^ fully polished and not at all tuberculate. The palpi tarsusof are of medium size. The tail is short; in the female, BROTEAS it is not so long as the body. This species is found in southern California. Family VEJOVIDiE (Ve-jov'i-dae) There is one spur on each side at the base of the last tarsal segment of the last pair of legs. There are three lateral eyes on each side. The sternum is usually broader than long, with a deep median furrow and with the lateral sides nearly parallel (Fig. 34). There is no spine under the sting. There are four genera Fi8'3' vSovii1 M °F of this family found in the United States: A. Middle area of the comb either indistinct or composed of not more than six pieces. 2Q Spiders and Their Near Relatives B. Lower margin of the movable finger of the chelicerae with about five teeth. The sting normal. P. 30. Uroctonus BB. Movable finger of the chelicerae with not more than three teeth. Sting of male swollen at base. (Fig. 36). P. 30. An UROCTONUS AA. Middle area of the comb divided into at least eight small pieces. B. No tooth on the lower margin of the movable finger of the chelicerae. Penultimate tarsal segment of the three front pairs of legs not strikingly clothed with bristles above. P. 31. Vejovis BB. A strong, brown tooth on the lower margin near the tip of the movable finger of the chelicerae. Penultimate tarsal segment of the three front pairs of legs with a comb of long bristles. P. 32. Hadrurus Genus UROCTONUS (U-roc-to'nus) The lower margin of the movable finger of the chelicerae is armed with about five teeth. The edge of the fingers of the chelae bear one long row of tubercles flanked by isolated tubercles (Fig. 35). The sting of both sexes is of the usual form. The lung-slits are nearly oval. Uroctonus mordax. — This is the only known species of this genus. It is found on the Pacific Coast. It attains a length of nearly two and one half inches. Fig. 35 FINGER OF UROCTONUS Genus AN UROCTONUS (A-nu-roc-to'nus) The movable finger of the chelicerae is furnished with not more than three teeth. The lung-slits are elongate. The sting of the male is swollen at its base (Fig. 36). Anurodonus phccodactylus (A. phae-o-dac'ty- lus). — This is the only known species of the genus. It has been found in Utah and in California. It Fig. 36. sting .. • , ., £ , , 1 ir • 1 OFANUROC- attains a length 01 nearly two and one half inches. tonus 30 Spiders and Their Near Relatives Genus VEJOVIS (Ve'jo-vis) There are no teeth on the lower edge of the claw of the chelicerae. The edge of the fingers of the chelae bears one long row of tubercles flanked by isolated tubercles. The last segment of the tarsus of the last pair of legs is furnished with a distinct empodium and with a row of short tubercles on the lower side. The middle area of the comb is composed of from eight to many rounded pieces. The fulcra are also rounded. The next to the last segment of the tarsus of the first three pairs of legs is not furnished with a comb of bristles. Banks ('oo) lists six species of this genus from our fauna and separates them as follows: A. Hand of the chelae with distinct ridges or keels and more or less granulate. B. On the under side of the first caudal segment the median keels are distinct and sharp, although fine, the sting is very slender and long. Occurs in the Far West. Vejovis puncfipalpi BB. There are no median keels on the under side of the first caudal segment or they are extremely indistinct, the sting is of ordinary length. C. The hand is strongly keeled, there are no keels on the hind tibiae, the colour is yellowish or greenish. Oc- curs from Nebraska to Idaho and in Utah and Nevada. Vejovis boreus CC. Hand less sharply keeled, hind tibiae with very plain keels, colour uniform reddish brown, legs paler. Occurs in Texas. Vejovis mexicanus AA. Hand smaller, without keels, the corners rounded and smooth. B. On the under side of the first caudal segment the median keels are plain, but not indicated by black lines, hand very slender, the fingers longer than in Vejovis spini- gerus, colour uniform yellowish. Occurs in New Mexico. Vejovis jLivus BB. No median keels on the under side of the first caudal segment or at most only indicated by black lines. C. Under side of cauda not very dark, the keels all indicated 3> Spiders and Their Near Relatives by black lines, palpi usually yellowish. Occurs in Texas, Arizona, and California. Vejovis spinigerus CC. Under side of cauda, with the whole of the dorsum and the palpi dark reddish brown; no black lines indicating the keels on the cauda, smaller than the preceding species. Occurs from South Carolina to Texas. Vejovis carolinus Genus HADRURUS (Had-ru'rus) There is a strong brown tooth on the lower margin of the movable finger of the chelicerae. The last segment of the tarsus with a large empodium. The penultimate tarsal segment of the three front pairs of legs with a comb of long bristles. Hadrurus hirsutus (H. hir-su'tus). — This is a very large and hairy species found in the Southwest. The penultimate tarsal segment of the first three pairs of legs is furnished with long hairs on the back. Order SOLPUGIDA* The Solpugids The order Solpugida (Sol-pu'gi-da) includes a small number of comparatively rare arachnids; only a few species occur in the United States, and specimens of these are rarely found; they occur in the southern and western portions of our territory. They are chiefly nocturnal and hide during the daytime, which may account in part for their unfamiliarity, but some are diurnal. Figure 37 will serve to illustrate the form of these strange arachnids. Their most striking features are the enormous size of the chelicerae, and the segmented condition of the thorax. In the latter respect they resemble the Microthelyphonida and the Shizonotidae already described; the segment bearing the second pair of legs (the fourth pair of appendages) being more or less distinct, and the segments bearing the last two pairs of legs * The name Solpugides was proposed by Leach in 1815 as a family name; it is now spelled Solpugida for the sake of uniformity with other ordinal names of Arachnida. The name Solifugae, which is used by some writers was proposed by Sundervall in 1833; there seems to be no good reason for substituting this for the older name. The name Galeodea, proposed for this order by Kirby and Spence in 1826, is used by some writers, evidently because the generic name Galeodes is older than the generic name Solpuga; but as the name Solpuga is still retained for one of the genera of this order, there appears no good reason fur adopting the latter ordinal name. 32 Spiders and Their Near Relatives resembling the abdominal segments in the degree of their dis- tinctness. This is doubtless a very generalized feature. The abdomen consists of ten segments, all of which are free. The beak, which bears the mouth at its tip, projects forward from between the basal segments of the pedipalps. There is a pair of eyes near the middle line on the front part of the head, and one or two vestigial eyes on each side of the head (Bernard '96). The chelicerae are two-jointed and chelate; compared to the size of the body, they are larger than in any other arachnids; and they are the only ap- pendages fitted for crushing the prey. "Observers re- late that, in order to bring the beak up to the wound in its prey, the animals work the chelicerae with a sawing motion, holding tight with one to drive the other deeper in." A peculiarity of these che- licerae is that the second segment is articulated to the lower side of the first segment, so that the pincers open and shut dorsoven- trally. In some forms each chelicera bears on its upper side a remarkable sensory appendage, which is called the JJ age Hum; this varies in shape greatly in the differ- ent genera; it has been thought that this organ is possessed only by males, but (Bernard '96) states that this is not certain. The function of the flagellum is unknown. The pedipalps are leg-like in form, but without claws. They bear no masticatory ridges; and it is evident that their chief function is that of feelers. At the tip of each pedipalp there is an invaginated sense organ (Bernard '96); these were formerly supposed to be suckers for clinging to objects. The first pair of legs have lost their locomotor function and doubtless resemble the pedipalps in function; their Fig. 37. EREMOBATES CINEREA (after Putnam) 33 Spiders and Their Near Relatives claws are vestigial. It might be said, therefore, that the sol- pugids have two pairs of pedipalps and only three pairs of legs. No other arachnids have two pairs of feelers. It will be re- membered that in the Pedipalpida, where the first pair of legs are developed into feelers, the pedipalps are fitted for crushing the prey. The remaining three pairs of legs are fitted for locomotion, and bear tarsal claws. The trochanters of the last pair of legs consist each of two segments. One of the most characteristic features of the solpugids are the racquet-organs, which are borne by the last pair of legs. These are T-shaped or racquet-shaped sense organs (Fig. 38), of which there are five on each hind leg, two on the coxa, two on the trochanter, and one on the femur. They have been described in detail by Bernard ('96). The respiratory organs are tracheae. There is a pair of spiracles behind the coxae of the first pair of ambulatory legs; and the second and the third abdominal segments each bear a pair of spiracles on the ventral side; these are covered by opercula. Sometimes the fourth abdominal racquet-organs segment bears a single, median spiracle. The opening of the reproductive organs is on the first abdominal segment, and is covered by a pair of opercula, which are regarded as vestiges of abdominal limbs. Most solpugids spend the day under stones or other rubbish or in holes in the ground, and come forth at night to seek their prey; but some species are diurnal. They occur chiefly in desert regions, but sometimes they enter houses. They feed on insects, and it is said that they will attack and "devour" small verte- brates such as lizards (Hutton '43). Captain Hutton states distinctly that the Galeodes observed by him consumed an entire lizard except the jaws and part of the skin. Other instances in which solpugids are supposed to have eaten their prey are given by the Rev. J. J. Wood, in his " Natural History Illustrated," and quoted by Murray ('77). Still it is believed that the solpugids take only liquid food, which they suck from the bodies of their victims. (Bernard '96, p. 357.) Professor Cook reports that in southern California they enter hives and capture honey-bees, both workers and drones. 34 Spiders and Their Near Relatives Pocock ('98) states that the females excavate subterranean burrows for the protection of themselves and their young. The process has been observed in the case of an Indian species. Choos- ing a suitable spot, the female proceeded to cut away the earth in a circle with her chelicerae, then kicked away the loosened fragments with her legs, or scraping them together into a heap with the pedipalps, pushed the pile by main force from the en- trance of the burrow. At its opposite end, the eggs, about fifty in number and resembling a mustard seed in size and shape, were laid; they hatched about a fortnight afterward. For three weeks the young showed no sign of movement. They then moulted for the first time and started to crawl about on their own account, little copies in miniature of their mother, who mounted guard at the entrance and resolutely repelled all intru- ders, snapping without hesitation at every object thrust into the burrow. The solpugids are exceedingly agile; on this account they have been called wind-scorpions, a name translated from the Arabic. One observer compares them to a piece of thistledown driven before the wind. "Often when going at full speed, in search for food, they will stop abruptly and begin hunting and feeling around a small spot, irresistibly calling to mind the be- haviour of a dog checked in mid-course by the scent of game. (Pocock, 98.) The Indian species referred to above is an expert climber, and has been seen to ascend trees to some height above the ground in search of prey. And it is also stated that in Egypt it is no uncommon thing to see Galeodes arabs climbing on to a table to get at the flies. To capture such quick and wary insects the solpugid adopts the tactics of the hunting-spider; instead of making a furious dart, as it would if the prey in sight were a beetle, it proceeds to stalk the flies in the most wary fashion, creeping toward them with such slowness and stealth that the movements of the legs are almost imperceptible, yet all the while drawing gradually nearer and nearer; then like a flash of light the inter- vening space is traversed, and the insect struck down and cap- tured. (Mr. A. Carter quoted by Mr. Pocock 98.) The solpugids are commonly believed to be venomous; but those who have studied them most carefully do not think that this is so. No poison glands have been found, and observers 35 Spiders and Their Near Relatives have allowed themselves to be bitten by solpugids without suffering anything worse than a passing pain from the wound. Among the more important works on the structure of these animals are those of Dufour ('62) and Bernard ('96); and a general work on their classification was published by Simon ('79). The species of the United States were studied by Putnam ('83), and an analytical synopsis of them is given by Banks ('00). Only twelve species are known to occur in our fauna; but doubtless more remain to be discovered. Our known species represent three genera, which can be separated as follows: A. Anterior margin of the cephalothorax truncate. B. Hind tarsi consisting of a single segment. P. 36. Eremobates BB. Hind tarsi three-jointed. P. 37. Hemerotrecha AA. Anterior margin of the cephalothorax subconical. p. 38. Ammotrecha Genus EREMOBATES (Er-e-mob'a-tes) In the members of this genus the anterior margin of the cephalothorax forms a transverse straight line or is slightly arched (Fig. 37); and the tarsus of the last pair of legs consists of a single segment. In the males the fixed finger of the chelicerae is straight and unarmed; and the flagellum is replaced by a strong bundle of setae. The name Eremobates now applied to the genus replaces the name Datames by which it has been commonly known; the name Datames was first applied to a genus of walking-sticks, Phasmidae, and can not be used for these solpugids. To the genus Eremobates belong eight of the twelve species of the order known to occur in the United States. These are separated by Banks ('00) as follows: A. Movable finger of the chelicerae of the male with two large subequal teeth with denticles between them. B. Some short conical spines under the tibia of the palpus in both sexes. Occurs in Colorado and New Mexico. Eremobates sulpburea 36 Spiders and Their Near Relatives BB. No such spines under the tibia in either sex. Occurs in New Mexico. Eremobates jormicaria AA. Movable finger of the cheliceras of the male with but one large tooth, others much smaller. B. Movable finger of the chelicerae of the male constricted from below near the apical third. Occurs in Arizona and California. Eremobates californica BB. Movable finger not constricted from below. C. The movable finger near the apical fourth is suddenly narrowed from above, very large species. Occurs in Arizona. Eremobates cinerea CC. If the movable finger is narrowed from above, it is much before the apical fourth. D. Only slender hairs on the inner side of the femur and tibia of the palpus of the male. Occurs in Kansas, Texas, Colorado, and Wyoming. Eremobates pallipes DD. Spine-like bristles on the inner side of the femur and tibia of the palpus of the male. E. Upper finger stouter than usual, narrowed near the tip, a small tooth near the middle of the movable finger, tips of palpi black. Occurs in Texas and Arizona. Eremobates magna EE. Upper finger slender throughout, no tooth near the middle of the movable finger. F. Small conical spines on the under side of the tibia of the palpus of the male. Occurs in California and Arizona. Eremobates formidabilis FF. No such spines on the tibia of the palpus of of the male. Occurs in California. Eremobates putnami Genus 1 IEMEROTRECHA (Hem-e-rot're-cha) The members of this genus resemble Eremobates in having the cephalothorax truncate in front; but differ in having the hind tarsi three-jointed. The male has an elongated flagellum con- sisting of two pieces lying along the inner side of the upper finger 37 Spiders and Their Near Relatives (Fig. 39). The upper finger of the male is without teeth; but there are several teeth on the basal half of the lower finger. Only a single species has been described; this is Hemerotrecba cali- fornica. It was found near Pacific Grove, California. The male meas- ures two fifths inch in length. The adult female is unknown as yet. Genus AMMOTRECHA (Am-mot're-cha) Fig. 3g. CHELICER/E OF HEMEROTRECHA The members of this genus are sharply distinguished from the other two genera found in our fauna by the subconical form of the anterior end of the cephalothorax (Fig. 40). The chelicerae are long and not so stout as in Eremobates. The fixed finger is armed with a row of unequal teeth. The name Ammotrecha has been substituted for Cleobis formerly applied to this genus, as the name Cleobis was preoccupied. Only three species of Ammotrecha have been found within the United States; these are separated by Banks ('00) as follows: A. Lower finger of the chelicerae finely, but distinctly, denticu- ■Y y' V-,IL,V'" Fig. 40. AMMOTRECHA CUB^ late beyond the large teeth (after Putnam) near its base; a broad dark band on the middle of the metatarsus of the palpus. Occurs in California. Ammotrecha californica AA. Lower finger not denticulate. B. Upper finger with a very plain ridge above at base, below there are several small teeth followed by three large subequal teeth. Occurs in Arizona. Ammotrecha peninsulana 38 Spiders and Their Near Relatives BB. Upper finger with a less distinct ridge, below there are two large teeth, a small one, then a large one. Occurs in Florida. Ammotrecha cubce Order ARANEIDA* The Spiders The order Araneida, which includes only the spiders, is discussed at length in the following chapters, to which the reader is referred. The order is mentioned here merely to indicate its position in the series of orders into which the Class Arachnida is divided. Order PSEUDOSCORPIONIDAf The Pseudoscorpions The pseudoscorpions (Fig. 41) are small arachnids which resemble scorpions in the form of their pedipalps and of their body, except that the hind part of the abdomen is not narrow, as is the postab- domen of scorpions, and they have no caudal sting. The body is flattened, which enables these crea- tures to live in narrow spaces, as beneath the bark of trees, between the leaves of books, and between boards in buildings. The cephalothorax is either un- segmented or crossed by one or two transverse furrows. The abdomen is broadly joined to the thorax; it is broad, flat, consists usually of eleven segments, and bears neither a sting nor a caudal appendage. On the ventral side of the cephalo- Fig. 41. PSEUDOSCORPION •The name Araneides was proposed by Latreille as a family name in iSoCi; it was changed to Ara- neidea by Leach in 1S17; and it is now spelled Araneida for the sake "I uniformity with other ordinal names of Arachnida. The form Aranea. which is used by some writers was introduced by Sundevall in 1833. t The original form of this name was Pseudoscorpitma, a family name proposed by Latreille in 1817. The family aaxat'jCherttettdlS proposed by Menge in 1855 is used by some writers as the name of the order; but it should be dropped. 39 Spiders and Their Near Relatives thorax, the coxae of the appendages meet on the middle line (Fig. 42) so that there are no traces of sternites except perhaps the labium and a triangular plate between the last pair of legs which is visible in some genera. The median eyes are wanting; there are only one or two pairs of lateral eyes; and in some forms even these are wanting. The beak is well-developed and con- sists of a labrum and a labium; the former is broad and extends down on each side of the narrow labium. The chelicera? are complicated in struc- ture, and as their variations in form afford VENTRAL^ASPECT OF CnaracterS that are mUch USed in dassifica- cephalothorax and tion, they merit a detailed description. of two abdominal Th are two-jointed and chelate; the SEGMENTS - J chela? are horizontal, the movable second segment or finger forming the lateral mem- ber of the pincers (Fig. 43). The movable finger of the chelicera bears on its lateral side near the tip a spinneret; in some s. forms this is simply a slight eminence on which the ducts of the silk glands open (Fig. 44); in others it is prolonged into a slender, more or less branched stylet (Fig. 43); and in a South American genus the finger of each chelicera bears three simple spinnerets. The elongated type of this organ is designated by different writers as process of the finger, as stylet, and as galea; but now that its function is known, the term spinneret is sug- gested as more descriptive and one which can be applied to all types of the organ. The finger of the chelicera bears also on its inner margin a comb-like organ, the serrula; this is either attached throughout its entire length to the finger (Fig. 43) or the distal part is free (Fig. 44). Balzan (91) divided the order into two suborders using these two types of the serrula as the distinguishing characters. Fig. 43- CHELICERA OF CHELIFER s, spinneret more en- larged /, flagellum 40 Spiders and Their Near Relatives The first segment of the chelicera bears on its under side an appendage, which is termed the jlagellum. In its most highly developed form, as seen in Chthonius (Fig. 44), the flagellum consists of a slender transparent stalk divided at its extremity into a greater or less number of branches, which may be simple or divided into secondary branches, and which are always clothed with fine hairs. In the simpler form as seen in Chelifer it consists of a row of three or four filiform appendages (Fig. 43/). The flagellum is extremely delicate and therefore difficult to study. The chelicerae function as spinning organs, and as such are discussed later. The pedipalps are enormously de- veloped and chelate, resembling those of scorpions. The chelae are furnished with scattered tactile hairs, which must serve as feelers. "The comparatively slow, deliberate manner of hunting prey may account for the fact that they re- quire no more specialized feelers than the pedipalps themselves, which are, as every one who watches them alive knows, highly sensitive" (Bernard '96). The coxae of the pedipalps are extended forward so as to form masticatory plates or they bear distinct endites; these serve to hold the prey in front of the mouth, and per- haps also function as jaws. All of the four pairs of legs are fitted for walking (Fig. 41). The seg- mentation of the legs in this order is somewhat different from the usual type in the Arachnida. The tibia is not divided, in other words a patella is wanting. On the other hand, with many pseudoscorpions, the femur consists of two, more or less distinct, segments; when this division exists, the proximal segment may be termed the second tro- chanter. This second trochanter is sometimes a very distinct segment (Fig. 4s a); but in other cases it is a triangular seg- ment, closely joined to the femur (Fig. 45 b), and resembling the trochanter of many beetles. This segment which I have designated the second trochanter Fig. 44- CHELICERA OF CHTHONIUS s, spinneret /, flagellum 41 Spiders and Their Near Relatives is commonly termed the trocbantin by writers on the Pseudo- scorpionida. But the word trochantin was first used in this sense by Blanchard in 1852, long after it had been in general use by entomologists in an entirely dif- ferent sense. The number of segments in LEGS OF CHELIFER a, fore leg b, hind leg i, coxa 2, trochanter 3a, second trochanter 3b, femur 4, tibia the tarsus varies from one to three. The praetarsus is usually distinct; and there are two tarsal claws. Below the claws there is a membranous empodium (Fig. 46). The respiratory organs are tubular tracheae, which open by two pairs of long slit-like spiracles on the second and third abdominal segments, on the ventral side near the lateral margins. In addition to these there are vestigial spiracles on all of the re- maining abdominal segments (Bernard '93). In the form of the respiratory organs the pseudo- scorpions differ greatly from the scorpions, near which they are commonly placed in the text-books. The opening of the reproduc- tive organs is on the middle line between the second and third ab- dominal sterna. The female carries the eggs about, attached to the abdomen; they are on the outer surface of a sac which is attached to the wall of the opening of the reproductive organs by a slender and broad pedicel, the whole forming a small raspberry-shaped mass. The sac is filled with food material; and the young when hatched are furnished with a long sucking beak by means of which they obtain the food thus supplied. They attain their definite form in this position. Fig. 46. TARSUS OF CHELIFER 42 Spiders and Their Near Relatives The transformations have been described by Metchnikoff ('71), Bouvier ('96), and Barrois ('96). Behind the opening of the reproductive organs there are two median papillae through which glands open, one at the anterior edge of the second abdominal segment and one in the corresponding place on the third abdominal segment. These were formerly believed to be silk organs; but the glands are now regarded as cement glands, which secrete the substance with which the eggs are fastened to the mother. These glands appear to develop periodically (Bernard '93). In the males there is borne by the first abdominal segment a pair of re- markable structures known as the ram's- horn organs. They are situated under the genital operculum, close to the genital aperture. In Fig. 42 the tips of these organs can be seen through the genital operculum; but they may be extended to great length, reaching to either the front or the hind end of the body as shown in Fig. 47 from Simon ('79)- The function of these organs has not been determined. Menge ('55) who first described them, believed that they Fig. 47. VEN- TRAL ASPECT OF CHELIFER SHOWING THE RAM'S-HORN ORGANS EX- PANDED \ J were sexual organs; but Croneberg ('88) and Bernard (93) suggest that they are respiratory. 1 he true silk glands were discovered by Croneberg ('87). They are situated in the cephalothorax and open through a group ol minute apertures near the tip of the movable finger of the chelicera, in the same position as the opening of the poison gland of spiders. In those forms in which the spinneret is long and branched the openings of the silk ducts are on the tips of the branches; in Obisium they open on a blunt prominence, which may be regarded as a rudiment of a spinneret ; in this case according to Bernard ('93a) there are about seven of these ducts in each chelicera. The silk spun by the chelicera? is used for the formation of a web or a cocoon in which the pseudoscorpion retreats during 43 Spiders and Their Near Relatives the moulting period and during the winter; sometimes earth is mixed with the silk in forming the cocoon. It is believed that the function of the serrula is the manipulation of this silk. Like the cement glands, the silk glands appear to be subject to periodic variations in their development; this is doubtless explained by the fact that they are needed only at certain and rather remote periods. The pseudoscorpions live under stones, beneath the bark of trees, in moss, under leaves on the ground, in the nests of bees, of ants, and of Termites, and in the dwellings of man, where they are often found between the leaves of books. In the South they have been beaten from leaves of palmetto. It is believed that they feed chiefly on mites, psocids, and other minute insects. They are often found attached to insects, especially to flies and to beetles. Most writers think that they do not feed on these large insects, but merely use them as means of rapid locomotion; but according to the observations of Berg ('93) the pseudoscor- pions kill the flies and eat them afterward. An excellent account of the order with descriptions of the species occurring in France was published by Simon ('79) and later Balzan ('91) gave a new and elaborate classification. There are many other European papers on the order; but I have found these two the most useful. Nearly fifty species representing eleven genera have been recorded from the United States; and it is probable that many more species remain to be discovered, as the order has been studied by onlv a few American entomologists. A synopsis of our recorded species was published by Banks C95&); and a list of them by Coolidge ('08). Following the classification of Balzan we have in our fauna representatives of three families; these can be separated as follows: A. Cephalothorax with a transverse median suture. P. 45. CHELIFERIDyt AA. Cephalothorax without a transverse suture. B. Serrula of the chelicera attached throughout its length to the movable finger. P. 45. Cheliferid/E BB. Serrula of the chelicera attached only at the base. C. Spinneret of the chelicera long, slender, and trans- 44 Spiders and Their Near Relatives parent.* Femur and tibia of the first two pairs of legs short and stout. P. 50. Ideobisiidve CC. Spinneret knob-like and of the same colour as the finger. Femur and tibia of the first two pairs of legs rather long and slender. P. 51. Obisiid^ Family CHELIFERIDiE (Chel-i-fer'i-dae) This family includes all those pseudoscorpions in which there is retained evidences of segmentation of the cephalothorax; in the other families the cephalothorax is without any transverse sutures on the dorsal aspect; and this is also true of some members of this family. Even in those genera in which the more typical species have well-marked transverse sutures there are species in which the sutures are indistinct. The presence of one or two transverse sutures in the cephalothorax clearly indicates that the species belongs to this family; but if such sutures be wanting, the position of the species must be determined by other characters. The members of this family differ from all other pseudo- scorpions in having the serrula attached throughout its length to the finger of the chelicera. The spinneret of the chelicera is long and delicate. The flageilum is absent. The tarsi of the legs are one-jointed; and the tarsal claws are short and thick and more or less split on some or on all of the feet. The following table will aid in separating the five genera representing this family in our fauna; but unfortunately the pres- ence or absence of a transverse furrow on the cephalothorax is sometimes difficult to determine. A. With only two eyes or with none; cephalothorax evenly rounded in front; anterior legs with a second trochanter. (Subfamily Cheliferinas.) B. Cephalothorax with a transverse suture. C. Femur of the palpus not pedicellate, gradually and slightly enlarged from base to tip; palpi very long and slender; eyes present except in cave species. P. 46. Chelifer CC. Femur of palpus distinctly pedicellate, being suddenly • According to Ranks ('95b) some males of the genus Ideoroncus "lack the stylet"— i. e., the spin- neret is short. I- Spiders and Their Near Relatives enlarged near the base; palpi short and stout; eyes usually wanting. P. 47. Chelanops BB. Cephalothorax without a transverse suture. P. 49. Atemnus AA. With four eyes; cephalothorax narrowed quite suddenly in front of the eyes; anterior pair of legs without a second trochanter. (Subfamily Garypinae). B. Cephalothorax with a transverse suture, although some- times it is indistinct; eyes remote from anterior mar- gin of the carapace. P. 49. Garypus BB. Cephalothorax without a transverse suture. Anterior eyes about their diameter from the anterior margin of the carapace. P. 50. Olpium Genus CHELIFER (Chel'i-fer) Seven species of Chelifer have been found in the United States. These can be separated by the following table which is based on one published by Banks C95&): A. Without eyes; the tibia of the pedipalp swollen on the inner side. This is a cave species, described from Kentucky and Virginia. Chelifer mirabilis AA. With two distinct eyes. B. Tibia of the pedipalp a little convex on the inner side; fingers a little shorter than the hand. This is a western species which has been found in Utah, California, and Oregon. Chelifer scabrisculus BB. Tibia of the pedipalp not convex on the inner side; fingers as long as the hand. C. Hand much darker than the other part of the palpus. Common in the East and the Middle West. Chelifer muricatus CC. Palpi unicolorous. D. Tibia of the pedipalp longer than the cephalothorax plus the chelicerae and distinctly concave on the outer side at the base. Known only from south- ern Florida. Chelifer floridanus DD. The tibia of the pedipalp not longer than the ceph- alothorax plus the chelicerae, the outer side not concave. 46 Spiders and Their Near Relatives E. Body red-brown; hand quite thick; larger gran- ules on the cephalothorax. F. Abdominal scutas each with a roughened ridge, most prominent in the males. Found in southern Arizona. Chelifer bubbardi FF. Abdominal scutae without a roughened edge. This is our most common and most widely distributed species. It is often found in houses. Chelifer cancroides EE. Body pale yellowish; hand more slender; no larger granules on the cephalothorax. This species was beaten from the leaves of palmetto in Florida. Chelifer biscriatum Genus CHELANOPS (Chel'a-nops) The genus Cbelanops is by far the largest of our genera, in- cluding nineteen of our described species. No complete table i)t" them has been published as yet; the following, based on one b\ Banks ('95 b.) will enable the student to determine most of the species: A. 1 lairs on the palpi very long and simple, abdomen long and of equal width throughout. This group is represented in our fauna by the two following species. B. Of moderate size; less than one eighth inch in length. A species well distributed throughout the Eastern and Southern States. Cbelanops oblongus BB. A much larger species found in Colorado and southern Arizona. .Cbelanops grossus AA. Hairs on the palpi short and thick often clavate, abdomen much the widest in the middle. B. Hand with a large tooth-like projection on the inner side. Cbelanops deniatus BB. Hand without any projection. C. Fingers as long or nearly as long as the hand. D. Hairs not distinctly clavate. E. Inner margin of the hand not greatly swollen at base. F. Fingers as long as or longer than the hand. 47 Spiders and Their Near Relatives G. Colour pale reddish yellow, soft parts white. Length one twelfth inch. Fingers a little longer than the hand. A species found along the seashore on Long Island, N. Y. Chelanops tristis GG. Cephalothorax very dark brown, abdominal scutae brown. Length of body one eighth inch. Fingers as long as the hand. A spe- cies found in southern Arizona. Chelanops ari%onensis FF. Fingers a little shorter than the hand. De- scribed from Isle Royale, Lake Superior. Chelanops morosus EE. Inner margin of the hand very much swollen at the base, so that the hand is nearly as broad as long. F. Palpi greenish. Occurs in Florida. Chelanops latimanus FF. Palpi nearly black. Described from Virginia. Chelanops virginica DD. Hairs distinctly clavate. E. Inner margin of hand greatly swollen at the base. F. Cephalothorax and palpi pale brownish yellow. Florida species. Chelanops tumidus FF. Cephalothorax and palpi dark brown. Cali- fornia species. Chelanops validus EE. Inner margin of the hand but weakly swollen ati the base. F. Palpi pale yellowish. G. Florida species. Chelanops affinis GG. A northern species. Chelanops pallidas FF. Palpi dark red-brown. G. Occurs in the East and Middle West. Chelanops sanborni GG. Occurs in the Far West. H. Length one eighth inch; finger about as long as the hand and slender. Chelanops pallipes HH. Length one twelfth inch; finger shorter and stouter than in C. pallipes. Chelanops dorsalis 48 Spiders and Their Near Relatives CC. Fingers much shorter than the hand. D. Two distinct eyes, hairs clavate. Described from Texas. Chelanops texanus DD. No eyes, hairs not clavate. E. Pacific Coast species. Chelanops acuminatus EE. Florida species. F. Chelanops floridce FF. Chelanops latus Genus ATEMNUS (A-tem'nus) The members of this genus are blind; they lack the transverse furrow on the carapace; and second trochanters are visible on all of the legs. A single species has been found in the United States. Atemnus elongatus (A. e-long-ga'tus). — The cephalothorax and legs are yellowish, the abdomen brownish, and the palpi red-brown. Cephalothorax smooth, one and one half times as long as broad. Length of body one eighth inch. This species has been found only in Florida. Genus GARYPUS (Ga-ry'pus) The cephalothorax is longer than wide and quite suddenly narrowed in front of the eyes; it is crossed by a transverse furrow, but this is sometimes indistinct; and there is a longitudinal median stria on the anterior part. The anterior pair of eyes are broadly separated from the anterior margin of the carapace. The scutze of the abdominal segments are divided by a median longitudinal suture. Only three species of this genus have been found in the United States; all of these were described by Mr. Banks, who separates them as follows: A. Cephalothorax with lateral ridges and prolonged anterio- lateral angles, second trochanters not distinct. Found in the Yellowstone National Park. Garypus bicornis AA. Cephalothorax without lateral ridges or prolonged angles; posterior legs with distinct second trochanters. B. Claw very much darker than the rest of the palpus. A large species, measuring one sixth inch in length, found in Florida. Garypus Jloridensis 49 Spiders and Their Near Relatives BB. Palpus all of one colour. A small species, measuring less than one twelfth inch in length, found at Ithaca, N. Y. Gary pus gr anu lat us Genus OLP1UM (Ol'pi-um) The cephalothorax is a little longer than wide and quite sud- denly narrowed in front of the eyes; it is marked by neither trans- verse nor longitudinal striae. The anterior eyes are separated from the anterior margin of the carapace by a space about equal to their diameter. The scutae of the abdominal segments are not divided by a median longitudinal suture. The following is our only known representative of this genus. Olpium obscurum (O. ob-scu'rum).— - This is a small blackish species measuring only one twelfth inch in length; it occurs in Florida. Family IDEOBSIID^E (Id-e-o-bi-si'i-dae) The members of this family resemble the Cheliferidae in having the spinneret of the chelicera long, slender, and trans- parent, but differ in having the serrula attached only at the base to the finger of the chelicera. The carapace is not divided by a transverse suture and the abdominal scutae are entire. The femur and tibia of the first two pairs of legs are short and stout. Representatives of two genera have been found in the United States; these can be separated by the number of eyes. A. With two eyes. p. 51. Ideoronchus AA. With four eyes. p. 50. Ideobsium Genus IDEOB1SIUM (Id-e-o-bis'i-um) The cephalothorax is smooth, without transverse sutures, nearly as broad in front as behind. There are four distinct eyes. The chelicerae are large, with a distinct spinneret. The abdomen is moderately elongate, with the scutae entire. The palpi are of moderate size, and with the fingers curved. The body bears simple hairs. Only two species have been found in the United States. Ideobisium rufuJum{\. ru'fu-lum). — In this species the cepha- SO Spiders and Their Near Relatives lothorax is distinctly longer than broad. It occurs in the Atlantic States. Ideobisium tbeveneti (I. thev-e-ne'ti).— - This is a common species in the States on the Pacific Coast. It differs from the preceding in that the cephalothorax is about as broad as long. Genus IDEORONCUS (Id-e-o-ron'cus) The species of this genus differ from those of the preceding in the possession of only a single pair of eyes. Ideoroncus obscunts (I. ob-scu'rus).— - This, our only species of the genus, is common in the Far West. It is a comparatively large species, the adult female often measuring one sixth inch in length. Family OBISIID^E (O-bi-si'i-dae) The members of this family are most easily recognized by the form of the spinneret of the chelicera, which is merely a small knob (Fig. 44); the serrula is attached only at the base; the caia- pace is not divided by a transverse suture; the abdominal scutae art entire; and the femur and tibia of the first two pairs of legs are rather long and slender. Four genera are represented in the United States; these can be separated as follows: A. Tibia of the pedipalp normal; chelicerae of medium size. (Subfamily Obisiinae.) B. With four eyes, except in cave forms; palpi short and stout. P. 51. Obisium BB. With no eyes; palpi very long and slender. P. 52. Blothrus AA. Tibia of pedipalp very short and cup-like; chelicera? very large. (Subfamily Chthoniinae.) B. With four eyes, except in cave forms; palpi long. P. 52. Chthonius BB. With only two eyes; palpi shorter. 1'. 5}. Lechytia Genus OBISIUM (O-bis'i-um) Five species of this genus have been found in the United States; they are separated as follows: 5> Spiders and Their Near Relatives A. With no eyes. A cave species described from Virginia. Obisium cavicola AA. With four eyes. B. Tibia of palpus with the inner side first convex, then nearly straight, fingers longer than the hand. C. Hand about twice as long as broad. A large species measuring one eighth inch in length. Described from North Carolina. Obisium carolinensis CC. Hand one and one half times as long as broad. A small species common in the Northern States. Obisium brunneum BB. Tibia of palpus with inner side evenly convex. C. Fingers very much longer than the hand. Found in southern California. Obisium macilentum CC. Fingers a little shorter than the hand. Supposed to have been found in Florida. Obisium parvulum Genus BLOTHRUS (Blo'thrus) Our only species of this genus, Blothrus calif ornicus , occurs in California. Genus CHTHONIUS (Chtho'ni-us) This and the following genus are remarkable for the great size of the chelicerae (Fig. 48). Six species of this genus have been found in this country, they are separated as follows: BB. Fig 48. CHTHONIUS MjESTUS A. With only two or with no eyes. B. Hind legs about twice as long as the abdomen. Found in caves in Kentucky and in Indiana. Chthonius packardi Hind legs not much longer than the abdomen. A cave species found in Virginia. Chthonius coccus AA. With four eyes. B. Cephalothorax and chelicerae with small spines, each tipped with a hair. Found in Florida. Chthonius spinosus 52 Spiders and Their Near Relatives BB. Without any spines. C. Eyes close together, almost touching. Found at Ithaca, N. Y. Cbtbonius mcestus CC. Eyes distinctly separated. I). Hind eye about twice its diameter from front eye; cephalothorax much wider in front than behind. Has been found in New York, Pennsylvania, and Florida. Cbtbonius pennsylvanicus DD. Hind eye not twice its diameter from front eye; cephalothorax but little wider in front than behind. Found in New York, District of Columbia, and Virginia. Cbtbonius longipalpus Genus LECHYTIA (Le-chyt'i-a; A single species of this genus, Lecbytia pacifica, has been found in the State of Washington. Order PHALANGIDA* The Harvestmen The harvestmen are very common in most parts of the United States. They are well-known to children in this country under the name daddy-long-legs, but as this term is also some- times applied to crane-flies, the name harvestmen is preferable. In some sections of the country the harvestmen are known as grandfather-graybeards. It was probably a misunderstanding of this name that led Wood ('68) to state that in northern New York they are called "Grab for Gray-bears." The writer spent his boyhood in northern New York and during that period heard only the name grandfather-graybeard applied to these creatures. The name harvestmen was probably suggested by the fact that they are most often seen at harvest time. A similar term, faucbeurs or hay-makers, is applied to them by the French. The Germans call them Afterspinncn or pseudo-spiders. ( )ther English names are harvest-spiders and shepherd-spiders. Most harvestmen can be recognized by their very long and * The original form of the name used above was Phalangita, a family name proposed by Latreille in 1802. It was chanced to Phalangides by Leach in 1815. It ia now spelled Phalangida for the sake of uniformity with the Other ordinal names of Arachnida. The name Opil tones, which is used by some writers, was proposed l>y MindevaU in 1833; there is no good reason lor substituting (his for the older name. 53 Spiders and Their Near Relatives slender legs (Fig. 49), although some species have comparatively short ones. The carapace is indistinctly if at all segmented. The abdomen is not constricted off from the cephalothorax and is short and broad. The sternites of the cephalothorax consist of a labium, which is well-developed in some forms and greatly reduced in others. (Photograph by M. V . Slingerland) Fig. 49- A HARVESTMAN and a sternum, which is more or less reduced as a result of either the approximation of the coxa? or of a forward thrust of abdominal sternites. The abdomen consists of nine segments, the anal tergite being the ninth. But the sternites of the abdomen are more or less reduced in number, sometimes to five, either by the con- solidation of two or more or by the suppression of some of them, or by both methods. The first abdominal sternite is termed the genital; the second, the tracheal; and the eighth the anal. "In many genera of the suborder Mecostethi the eighth abdominal Spiders and Their Near Relatives sternite shows indications of being composed of two sternites, which would bring the total number of sternites up to nine, thus equalling the tergites in number." (Pocock '02.) The various forms of the labium, the sternum, and the sternites of the first two abdominal segments afford characters for limiting the larger divisions of the order. The eyes are only two in number in our species and are sit- uated on a prominent tubercle, like a lookout tower, near the middle of the cephalothorax, an eye looking out on each side. Near the anterior margin of the cephalothorax, on each side opposite the attachment of the first pair of legs, there is a small opening; these are sometimes called the lateral pores and some- times' the openings of Krobn's glands. They are the openings of scent glands which have been described by Krohn ('67) and by Rossler ('82). The respiratory organs are tubular tracheae, which open by a pair of spiracles situated on the ventral side at the juncture of the lateral margins of the cephalo- thorax and the second abdominal ster- nite. Secondary spiracles have been found on the legs of some members of this order by Hansen (See Loman '96). The reproductive organs open on ., , , ,. . , , Fig. so. CADDO AGn.IS WITH the boundary between the cephalo- the ovipositor exposed thorax and the abdomen on the middle line of the ventral aspect of the body; the opening is covered by a prolongation of the sternite of the first abdominal segment, which is called for this reason the genital sternite. The female is provided with a large ovipositor, and the male with a large penis; each of these structures is usually retracted within a sac. The form of these organs varies in differenl species and has been used by systematists for distinguishing species. It is well therefore to' preserve specimens with these organs exposed (Fig. 50). This is "a simple operation, requir- ing only that the abdomen of the living specimen be compressed between the thumb and finger, when these organs will be extruded. and if the specimen is immediately chopped into alcohol will or- dinarily remain exposed" (Weed '89a). As the first abdominal sternum is thrust far forward the opening of the reproductive organs in some tonus is not far removed from the mouth. 55 Spiders and Their Near Relatives It is not as easy to distinguish the sexes of harvestmen as it is those of spiders, where a glance at the palpi is sufficient. With some harvestmen there are no obvious secondary sexual characters; but with most of them the sexes differ in size, coloura- tion, and the proportions of the appendages. Usually the body of the male is smaller and shorter and more brilliantly coloured than that of the female; but the markings of the female are often replaced by a uniform tint in the male. The granulations and spines are usually more marked in the male; and the legs are usually longer. The form of the chelicerae and of the pedipalps often differ in the two sexes, but no general statement can be made of these differences. The chelicerae are three-jointed and chelate, the third joint forming the finger of a chela. They are comparatively long and in some forms they are quite stout. The pedipalps are leg-like in form; but are much shorter than the legs; a tarsal claw is usually present; the coxae of the pedipalps bear endites, which are more or less membranous. A similar pair of more or less membranous endites are borne by the coxae of the first pair of legs. These two pairs of endites have been described as two pairs of jaws but in the forms examined by the writer they are hardly fitted for chewing. The legs are very long and slender except that the coxae are stout; but the coxae on account of their fixed condition appear to belong to the body instead of to appendages; the first two pairs of legs bear movable endites in some forms. The tarsi and sometimes other segments of the legs are divided into smaller portions by what are termed false articulations. The tarsal claws vary in number and in form. Although the harvestmen have stilt-like legs, they do not raise the body much above the ground when they walk, but carry it low down, with the middle part of their legs high in the air. When disturbed they stand on six legs and move the second pair about in the air; this suggests that perhaps the tips of the second pair of legs are furnished with especially sensitive tactile organs. In the North most harvestmen die in the autumn; a single species, Leiobunum formosum, is known to live over the winter as an adult instead of depositing eggs and dying in the autumn, as do the other species (Weed' 89 a). In the South more of them hibernate; they hide under rubbish during the winter. 56 Spiders and Their Near Relatives The eggs are laid in the ground, under stones, or in crevices of wood. They are placed in position by means of the ovipositor which can be extruded to a great length (Fig. 50). Henking ('88) figures a female in the act of depositing her eggs in the ground, and represents the ovipositor three times as long as the entire body of the animal. Unlike the eggs of spiders, those of the harvestmen which are laid in the autumn do not hatch till the following spring. The species observed by Henking remained six months in the egg. The young moulted as soon as they reached the surface of the ground; they were white as snow except the eyes, which were coal-black; the abdomen was pointed behind showing a one- jointed vestige of a postabdomen. In a short time the body becomes of the same colour as the adult. The newly hatched young use the second pair of legs as feelers in the same way as does the adult; but they are apt to hide under stones or other objects and rarely attract attention till midsummer, when they are more conspicuous. The adults also ordinarily hide during the day, but at twilight wander about in search of food. Some species apparently often migrate from the fields where they were hatched to the vicinity of houses, barns, and out-buildings where they congregate in large numbers; occasionally they congregate in a similar manner on the trunks of trees. It was said long ago by a German writer that "they spring and pounce upon their victim as the cat upon the mouse, and seize it with their palpi as if with hands." This is perhaps the foundation for the statement made in many books that the harvestmen feed on living insects. But Henking ('88), who kept large numbers of them under as nearly as possible natural con- ditions, found that they shunned living insects and fed only on those that they found dead. They also fed on various kinds of soft vegetables and fruits, from which they pressed the fluid by means of their chelicerae. On the other hand, Weed ('93). states that Liobnnum politum when in confinement eagerly devours plant lice; and Banks ('01) states that they feed mostly on living insects. It is also often stated that the harvestmen eat solid food. 1 his, however, needs confirmation. Bernard ('96) found, in some sections of an unknown Phalangid, that behind the brain 57 Spiders and Their Near Relatives the oesophagus formed a large muscular "crop" which was full of solid particles. As there were none in the stercoral pocket, he concluded that this is some special arrangement of the sucking- apparatus and that the solid matter is again ejected through the mouth. It has been suggested that the great length of the legs com- bined with the fact that they easily separate from the body serves as a means of protection from such animals as would prey upon the harvestmen. The body is fenced in, as it were, by a hedge of legs. In attempting to capture the harvestmen the enemy is almost certain to seize hold of a leg and to be left with only it in its grasp. It is probable that this means of protection is only brought into play as -a last resort; for they appear to have few enemies. This is doubtless due to the odour of the fluid secreted by the scent glands. The protective fluid is often excreted in considerable quantity, so as to be readily seen, when these creatures are handled. No silk glands have been found in this order; and harvestmen make no nests or retreats. The chief works on the harvestmen of the United States are those of Wood ('68), Weed ('92/7 and '93), and Banks ('93^, '93ft, '94^, and '01). In the last cited paper Banks gives a synopsis of our species which has been of great service in the preparation of the following account of them. The European works which I have used most are those of Simon ('79), Pocock ('02), and Cambridge ('04 -'05). The order Phalangida is divided into three suborders; one of these, the Cyphophthalmi, is not represented in our fauna; the other two can be separated as follows: A. Sternum of the first abdominal segment not reaching in front of the hind coxae. P. 58. Mecostethi AA. Sternum of the first abdominal segment extending much in front of the hind coxae. P. 64. Plagiostethi Suborder MECOSTETHI (Mec-os-te'thi) In this suborder the sternum of the first abdominal segment extends but little if any in front of the hind coxae and the sternum of the cephalothorax is narrow and long, lying between the coxae 58 Spiders and Their Near Relatives of the first three pairs of legs (Fig. 51). It is to this fact that the subordinal name Mecostethi refers, being derived from the Greek words mekos, length, and stcthos, breast. The hind tarsi are either furnished with two claws or with a compound claw; the tibia and tarsus of the pedipalps are more or less depressed; and the hind legs are usually the longest. This suborder is called the Laniatores (Lan-i-a-to'res) by some writers. The suborder Mecostethi is repre- sented in our fauna by two families, which can be separated as follows: —s. Fig. si. VENTRAL ASPECT IF CYNORTA SAYI s, spiracle A. Hind coxae united to the first abdominal segment at the base, but free at the apex; the spiracles are obscure. P. 61. Phalangodid/e AA. Hind coxae united to the first abdominal segment throughout their length; the spiracles are distinct. P. 59- Cosmetid^e Family COSMETIDiE (Cos-met'i-dae) The second pair of legs are without endites. The pedipalps are shorter than the body, with the tibia and tarsus depressed, and with the tarsal claw about half as long as the tarsus. The pedipalps are usually appressed to the face so as to fit over the chelicerae. The eye-tubercle is low, without coniform tubercles. The spiracles are exposed. Genus CYNORTA (Cy-nor'ta) The genus Cynorta, our only representative of the Cosmetidae, is a subtropical genus. Three species belonging to it have been found in the warmer portions of the United States. These can be separated as follows: A. With a pair of prominent lobes near the hind end of the cara- paceeach having a prominent acute spine. Cynorta ornata AA. Without prominent lobes near the hind end of the carapace. B. With two small rounded tubercles near the hind end of the carapace. Cynorta sayii 59 Spiders and Their Near Relatives BB. With neither spines nor tubercles near the hind end of the carapace. Cynorta bimaculata Cynorta sayii (C. say'i-i). — This is our most widely distrib- uted species of the genus, occurring in the Gulf States and extending as far north as Missouri and Kansas. The body is nearly one fourth inch in length, of a rusty colour mottled with a darker shade. In well-marked individuals there is a Y-shaped yellow strip back of the eyes (Fig. 52) and a transverse band near the hind edge of the cara- pace. The stem of the Y is sometimes wanting and some- times it extends to the trans- verse band. Between the arms of the Y and the transverse band there is in some individuals in- dications of two other transverse bands. Sometimes all of the white marks are wanting. Near the middle of the carapace there is a pair of small tubercles, and there is a second, somewhat larger pair near the hind margin just in front of the transverse yellow band. Cynorta ornata (C. or-na'ta). This species closely resembles the preceding in size and markings, but can be easily distinguished by the presence of a pair of prominent acute spines borne on a pair of lobes in the position occupied by the second pair of tubercles in the preceding species (Fig. 53). This species is found in the southeastern part of the United States. Cynorta bimaculata (C. bi-mac-u-la'ta).— - This is a smaller species, measuring one sixth inch in length, found in southern California. The dorsum is brownish red, with two long, some- what lunate white spots near the end of the carapace; the venter is red. The body is finely granulate, without large tubercles or spines. 60 Fig. 52. CYNORTA SAYII Spiders and Their Near Relatives Family PHALANGODID^E (Phal-an-god'i-dae) In this family the hind coxae are united to the first abdominal segment at the base, but are free at the apex. The second pair of legs have distinct endites. The pedipalps are robust and about as long as the body. The spiracles are indistinct. Our Phalangodidae represent five genera; these can be separated by the following table: A. Tarsus of the last pair of legs furnished with a simple single claw. P. 61. Cyptobunus AA. Tarsus of the last pair of legs furnished either with a compound claw or with two simple claws. B. Tarsus of the last pair of legs with one compound claw; palpi not as long as the body; eyes present. P. 63. BB. Tarsus of the last pair of legs with two simple claws. C. Eye-tubercle arising from the anterior margin of the cephalothorax; palpi shorter than the body. P. 04. Sitalces CC. Eye-tubercle back from the margin of the cephalo- thorax; palpi longer than the body. D. Tarsus of the second legs about twice as long as the body, its segments very slender; eyes absent. P. 64. Phalangodes DD. Tarsus of the second legs about as long as the body; eyes often present. P 62. Scotolemon Fig. 53. CYNORTA ORNATA SCLEROBUNUS Genus CYPTOBUNUS (Cyp-to-bu'nus) d. Fig. 54. CYPTOBUNUS CAVICOLUS a, body and cheliccra.- b, tibia of pedipalp r. tarsus of pcdipalp d, tarsus of leg (after Banks') The only known representative of this genus was recently discovered by Professor Coolev in a cave in .Mon- tana and was de- scribed by Mr. Banks. It differs Spiders and Their Near Relatives from all other members of this suborder in having the posterior tarsi armed with a single simple claw (Fig. 54J). The legs are very slender; the second pair are plainly longer than the fourth. The eye-tubercle is rather large, not very high, rounded, with two large black eye-spots above. The tibiae and tarsi of the palpi are depressed and armed laterally with long, slender spines, each spine consisting of a basal part, truncate at tip and a long terminal bristle arising beneath a short spur or apophysis (Fig. 54b). Cyptobunus cavicolus (C. ca-vic'o-lus). — This is a pale whitish nyaline species, with black eye-spots. Figure 54a represents the outline of the body. The length of the body of the only known specimen is less than one twelfth inch. Genus SCOTOLEMON (Sco-to-le'mon) The eye-tubercle arises some distance back from the anterior margin of the carapace but not far from it. Eyes are present in some species, absent in others. The pedipalps are longer than the body. The tarsus of the second legs is about as long as the body; and the tarsus of the fourth legs bears two simple claws. Four species have been found in the United States; these can be separated as follows: A. Eye-tubercle ends in a spine. Scotolemon spinifera AA. Eye-tubercle without spine. B. Colour pale yellowish or straw-yellow. Cave species. C. Tarsus of the second legs with short segments. Scotolemon Jlavescens CC. Tarsus of the second legs with long slender segments. * Scotolemon calijornica B.B. Colour yellowish brown; not cave species. Scotolemon brunnea Scotolemon spinifera (S. spi-nif'e-ra).— - This species is easily distinguished from our other three species of the genus by the form of the eye-tubercle, which ends in a high, sharp, prolonged spine. The eyes are black and placed unusually far apart. The body is spiny. This harvestman was found in Florida. Scotolemon calijornica (S. cal-i-for'ni-ca). — The colour is pale 62 Spiders and Their Near Relatives yellowish with the dorsum of the abdomen rather darker. The eye-tubercle is low, rounded, close to the anterior margin, but bears no eyes. Length of body less than one twelfth inch. The species was described from specimens taken in Alabaster Cave, California. Scotolcmon jlavescens (S. flav'es-cens). — Body broad and stout uniformly straw-yellow, including the appendages. The eye- tubercle is large and high; the eyes are distinct, black, and situated near the base of the conical tubercle. Pedipalps less than twice as long as the body, but nearly twice as long as the cephalothorax. Length of body one eighth inch. This is a cave species found in Kentucky, Indiana, and Virginia. Scotolemon brunnea (S. brun'ne-a). — Body yellowish brown, shield of abdomen mottled with irregular blackish markings, posterior margins of ventral segments, and of the last few dorsal segments margined with black. Eye-tubercle large, but blunt, and not far from the anterior margin of the carapace. Length of body one twelfth inch. This species occurs in North Carolina; it was found by sifting damp leaves in the woods. Genus SCLEROBUNUS (Scler-o-bu'nus) The posterior tarsi are armed with a single claw but it is a compound one, there being a spur or branch-claw on each side toward the base. The palpi are not as long as the body. The eyes are present. Two species have been found in the West. These can be separated by difference in colour. A. Colour red, tips of legs black. Sderobunus robustus AA. Colour brown, tips of legs yellowish. Sderobunus brunneus Sderobunus robustus (S. ro-bus'tus). — The colour of the bod is deep reddish, with the hinder segments finely bordered with brown. Body pyriform, two thirds as broad as long. Length of body one seventh inch. Sderobunus brunneus (S. brun'ne-us). — The colour of the body is brown, paler on the cephalothorax; legs brown, a little darker than the body, their tips yellow. The dorsum and legs have many little tubercles, each tipped with a stiff hair or bristle. 1 he legs are very short. Length of body one twelfth inch. 63 Spiders and Their Near Relatives Genus SITALCES (Si-tal'ces) The eye-tubercle arises from the anterior margin of the carapace. The pedipalps are shorter than the body. The tarsus of the fourth legs bears two simple claws. Sttalces calif ornicus (S. cal-i-for'ni-cus). — The colour of the body is yellow, venter paler, legs whitish toward the tips. Body oval, truncate in front, rounded behind. Eye-tubercle large, arising from the anterior margin of the carapace, and about one half as long as the cephalothorax, much roughened and finely granulated; eyes near the base of the tubercle. Legs short. Length of body one twelfth inch. Occurs in southern California. Genus PHALANGODES, (Phal-an-go'des) The eye-tubercle arises some distance back from the anterior margin of the carapace, but it bears no eyes. The pedipalps are longer than the body. The tarsus of the second pair of legs is about twice as long as the body, and the tarsus of the fourth pair of legs bears two simple claws. Phalangodes armata (P. ar-ma'ta). — This, our only species of the genus, is found in the Mammoth Cave and in other caves. The body is from one eighth to one sixth inch in length. All of the legs are re- markably long and slender. The colour of the adult is whitish straw-yellow, of the young, white. Suborder PLAGIOSTETHI (Pla-gi-os-te'thi) In the members of this suborder the sternum of the first abdominal segment extends much in front of the hind coxae (Fig. 55). A result of this forward thrust of this sternite is that the sternum of the cephalothorax is short and transverse; this suggested the name Plagiostethi, which is from the Greek words plagios, transverse, and stcthos, breast. The tarsi of the legs are furnished each with but one simple claw; the tibia and tarsus of the pedipalps are cylindrical; and the second legs are the 64 Fig. 55. VENTRAL ASPECT OF LEIOBUNUM VENT- RICOSUM Spiders and Their Near Relatives longest. This suborder is called the Palpatores (Pal-pa-to'res) by some writers. The Plagiostethi includes five families, four of which are represented in the United States; these can be separated by the following table: A. Last segment of the pedipalp with a claw at the end, this segment longer than the preceding one except in the male of Protolopbus. P. 65. Phalangiid/e AA. Last segment of palpus with no claw at the tip, this segment much shorter than the preceding one. B. Ocular tubercle prolonged into a plate which extends beyond the front margin of the cephalothorax. P. 79. TrOGULID/'E BB. Ocular tubercle not prolonged into a plate. C. Chelicerae very long, longer than the body. P. 76. IsCHYROPSALID/E CC. Chelicerae of moderate length. P. 77. Nemastomatid/e Family PHALANGIID/E (Phal-an-gi'i-dae) In the Phalangiidae the last segment of the pedipalps is much longer than the penultimate one and is armed with a small claw; the coxa of the fourth leg is united near its base on the posterior side to the tracheal sternite of the abdomen; the endite of the second leg is directed horizontally inward; and tibial spiracles are present. The genera of the Phalangiidae occurring in our fauna are separated by Banks ('01) as follows: A. Male with the palpus enlarged, last joint shorter than the penultimate; female with the patella of the palpus provided with a long branch; palpal claw smooth; a row of teeth on sides of coxae. P. 67. Protolopus AA. Last joint of palpus longer than the penultimate; patella of palpus without a branch in the adult. B. Eye-tubercle of enormous size; three long spines on the femur of the palpus. P. 68. Caddo BB. Eye-tubercle of normal size. 65 Spiders and Their Near Relatives C. A group of spinules on the anterior margin of the cephalothorax and the eye-tubercle spinose; palpal claw smooth; rarely if ever with lateral rows of teeth on coxae; frequently with spines on the femur of the palpus. D. Femur of palpus provided with prominent spines. E. No false articulations in the metatarsus of the first legs; eye-tubercle more remote from the an- terior margin. P. 70. Lacinius EE. At least one false articulation in the metatarsus of the first legs; eye-tubercle nearer to the margin. P. 70. Oligolophus DD. Femurof palpus not furnished with prominent spines. E. Femora and tibiae of the first and third pairs of legs thickened; coxa of the second legs com- pletely shut out by those of the first and third legs. P. 71. Globipes EE. Femora and tibiae of the first and third legs normal ; coxa of the second legs not shut out by those the first and third legs. F Two prominent supracheliceral teeth; dorsum punctate. P. 71. Homolophus FF. No such teeth. G. The femur of the first legs longer than the width of the body. P. 69. Phalangium GG. The femur of the first legs shorter than the width of the body. P. 69. Mitopus CC. Either with the eye-tubercle smooth or, if spinose, then no group of spinules on the anterior margin of the cephalothorax. D. Palpal claw denticulate; adult with a row of teeth on the sides of the coxae, distinct at least on the anterior side of the coxae of the first pair of legs; legs usually long. E. Body very hard and granulate above and below; legs very short; fourth pair of legs nearly as long as the second pair. P. 76. Mesosoma EE. Body softer, although often subcoriaceous; rarely granulate below; legs longer, fourth pair much shorter than the second pair. 66 Spiders and Their Near Relatives F. Femur of the first pair of legs longer than the body or in some females a little shorter, but longer than the width of the body. P. 73. Leiobunum FF. Femur of the first legs shorter than the body, in females not so long as the width of the body. P. 75. Hadrobunus DD. Palpal claw smooth; no such rows of teeth on coxae; legs usually shorter. E. Inner margin of patella of pedipalps extended; body very hard and rough; eye-tubercle spinose; coxae of the third and fourth pairs of legs enlarged in the males. P. 72. Trachyrhinus EE. Inner margin of patella of pedipalps not extended, or at least with the body quite soft. F Legs slender and long as in Leiobunum; coxae of the second legs not shut out by the coxae of the first and third pair of legs. P. 73. Leuronychus FF. Legs much shorter; femora of the first pair of legs thickened or not as long as the width of the body; eye-tubercle smooth. G. Femora and tibiae of the first and third pairs of legs thickened; coxa of the second legs shorter than that of the first. P. 72. Eurybunus GG. Femora and tibiae of the first and third pairs of legs not thickened; coxa of the second legs about as large as that of the first. P. 71. Leptobunus Genus PROTOLOPHUS (Pro-tol'o-phus) This genus differs from all other members of the Phalangiidae occurring in our fauna in having the last segment of the pedipalps of the male shorter than the penultimate, and in that the patella of the pedipalps of the female is provided with a long branch. There is a median pair of large tubercles on the dorsal aspect o\ each of the first five abdominal segments. Two species are found in the Far West. 67 Spiders and Their Near Relatives Protolophus tuberculatus (P. tu-ber-cu-la'tus). — The cephalo- thorax is gray, the dorsum of the abdomen darker, somewhat reddish brown; there is a broad, darker, median strip, extending from the anterior margin of the cephalothorax to the sixth ab- dominal segment. The abdominal tubercles are unarmed. Oc- curs in Texas and California. Protolophus singularis (P. sin-gu-la'ris). — This species is similar to the preceding but differs in that the abdominal tubercles bear from two to four spines. Occurs in California. Genus CADDO (Cad'do) The eye-tubercle is of enormous size, covering the greater part of the cephalothorax (Fig. 56); it is wider than long, smooth, with a broad median furrow. The eyes are very large and situated at each side of the ocular tubercle. Only two species are known. Caddo agilis (C. ag'i-lis). — This is the larger of the two species, attaining Fig. 56. CADDO AGILIS , . , f • . u , t-m i s a length of one sixth inch. 1 he colour is brownish with a silvery white longitudinal median band. The trochanter of the pedi- palps is armed below with only scattered stiff hairs. The femur of the pedipalps is armed with three large spine-tipped tubercles which are evenly spaced on the basal half (Fig. 57a). This species has been found in New York, District of Columbia, and Ontario. Caddo boopis (C. bo-o'pis). — The length of the body is only about one twenty-fifth of an inch. The color is dark brownish without the white median band. The trochanter of the pedipalps is armed beneath with a large tubercle bearing two spines, one large and one small. The femur of the pedipalps bears three large spines, two close together near the base and one near the middle of the segment (Fig. 576). As yet this species has been found only at Ithaca, N. Y. It was taken by Professor Crosby in sifting leaves on a heavily wooded bank. 68 Fig. 57. TROCHANTER AND FEMUR OF THE PEDIPALP OF a, Caddo agilis b, Caddo boopis Spiders and Their Near Relatives Genus PHALANGIUM (Pha-lan'gi-um) The last segment of the pedipalps is longer than the penul- timate, and the femur of the pedipalps is not furnished with prominent spines; there is a group of spinules on the anterior margin of the cephalothorax and the eye-tubercle is spinose; and the femur of the first legs is longer than the width of the body. Two species occur in the United States. Phalangium longipalpis (P. lon-gi-pal'pis). The palpi are very long, in the male they are longer than the body, in the female they are longer than the width of the body; the second segment of the chelicera of the male is prolonged above in a spur, that of the female is normal. The length of the body is a little over one fourth inch. The species was described from Arkansas. it occurs abundantly in New York. Phalangium cinereum (P. ci-ner'e-um). — The palpi are much shorter than in the preceding species, in the female they are scarcely as long as the width of the body; the chelicerae of the male are normal. The length of the body varies from one fifth to a little more than one fourth inch. This species is widely distributed in the Northern States. Weed in writing of it states as follows: 'This species is pre- eminently what may be called an indoor form. It abounds especially in sheds, outhouses, and neglected board-piles, being rarely found in the open field. Its colour especially fits it for crawling over weather-beaten boards, making it inconspicuous against such a background. During the day it is usually quiet, but at dusk and on cloudy days it moves about quite rapidly." Genus M1TOPUS (Mit'o-pus) The harvestmen of this genus agree with Phalangium in the characteristics given above except that the femur of the first legs is shorter than the width of the body. Three species occur in our fauna. Mitopus californicus (M. cal-i-for'ni-cus). — The tibia of the second legs is much longer than the metatarsus of these legs; there is one false articulation in the metatarsus of the first legs; and the eye-tubercle is about its diameter from the anterior margin of the carapace. The species occurs in California. 69 Spiders and Their Near Relatives Mitopus dorsalis (M. dor-sa'lis). — In the second legs the tibia is subequal to or shorter than the metatarsus; there is no false articulation in the metatarsus of the 'first legs; the colour of the body is gray and white. This is an Alaskan species. Mitopus montanus (M. mon-ta'nus.) — This species agrees, with the preceding in having the tibia of the second legs subequal to or shorter than the metatarsus; but differs in having two false articulations in the metatarsus of the first legs and in being brown or black and white. It occurs in New Hampshire. Genus LACINIUS (La-cin'i-us) In this and in the following genus there is a group of spinules on the anterior margin of the carapace, the eye-tubercle is spinose, the palpal claw is smooth, and the femur of the palpus is provided with prominent spines. In this genus there are no false articula- tions in the metatarsus of the first legs, and the eye-tubercle is more remote from the anterior margin than in the following genus. Lacinius texanus (L. tex-a'nus). — The metatarsi of the first and third legs are banded in the middle, and there are very promi- nent spines at the tips "of the femora and patellae. Occurs in Texas. Lacinius ohioensis (L. o-hi-o-en'sis). — The metatarsi of the first and third legs are not banded; the legs are longer than in the preceding species and the spines at the tips of the femora and patellae are less prominent. Occurs in the Eastern and Middle States. Genus OL1GOLOPHUS (Ol-i-gol'o-phus) There is a group of spinules on the anterior margin of the cephalothorax and the eye-tubercle is spinose; the palpal claw is smooth; the femur of the palpus is armed with prominent spines; and there is at least one false articulation in the metatarsus of the first leg. Oligolophus pictus — -The colour of the dorsum is mottled ash-gray with a dark central band extending the whole length of the body; this band is suddenly contracted near the posterior margin of the cephalothorax, then gradually expanded until it reaches the end of the anterior third of the abdomen, where it is suddenly contracted; behind this point the band is again widened 70 Spiders and Their Near Relatives and contracted. The body measures about one fifth inch in length. This species is found in New England: and is abundant in New York. Genus HOMOLOPHUS (Ho-mol'o-phus) There are quite prominent spines upon the cephalothorax and eye-tubercle and transverse rows of them on the abdomen. The legs are thicker than usual, the anterior femora being much thicker than the eye-tubercle is wide. There are two prominent supracheliceral teeth. Homolophus biceps (H. bi'ceps). — The dorsum is pale brownish with a great many small white spots and darker brown punctures; eye-tubercle with a broad white stripe above; and there is a bifid white stripe from the eye-tubercle to the anterior margin ; venter, sternum, and coxae whitish; spiracles and some spots on the venter brown. The male measures one sixth inch in length; the female, one fifth. Occurs from Colorado to Washington State. Genus GLOB I PES (Glob'i-pes) The principal character of this genus is the enlarged femora and tibiae of the first and third pairs of legs; the eye-tubercle is low and with a few spines; the legs are short; but the femur of the second legs is longer than the body and more than twice as long as the femur of the first legs. There are no false articulations in the metatarsus of the first legs. The palpi are normal. A single species has been described. Globipes spinulatus (G. spin-u-la'tus).— - The colour of the body is brown or reddish brown, tip of abdomen more gray, dorsum somewhat mot lied with brown. The female has two median white spots near the tip of the abdomen. Length of body one seventh inch. Occurs in California. Genus LEPTOBUNUS (Lep-to-bu'nus) The legs are short, with the segments but little thickened: the femur of the first legs is much shorter than the body; frequently the femur of the second legs is not as long as the body. The eye-tubercle is narrow and is usually smooth. Two western species have been described. 71 Spiders and Their Near Relatives Leptobunus borealis (L. bo-re-a'lis). — The apices of the coxae are dark; the tibia of the first legs is marked with one dark band; the palpus is lineate with brown. Occurs in Alaska. Leptobunus californicus (L. cal-i-for'ni-cus). — The apices of the coxae are pale; the tibia of the first legs is marked with two dark bands; and the palpus is not lineate. Occurs in California. Genus EURYBUNUS (Eu-ry-bu'nus) The eye-tubercle is very low and smooth; the cephalothorax with an elevation on the anterior margin bearing a few small spines. The segments of the dorsal shield of the abdomen are so closely united that their sutures are hardly discernible. The femora, patellae, and tibiae of the first and third legs are enlarged; the femur of the second legs is barely twice as long as that of the first legs, and a little longer than the body; the metatarsus of the first legs is without false articulations. Eurybunus brunneus (E. brun'ne-us). — The body is very smooth; the fourth leg is nearly as long as the second. Occurs in California. Eurybunus spinosus (E. spi-no'sus). — The body is armed with transverse rows of spinules; the fourth leg is much shorter than the second. Occurs in California. Eurybunus formosus (E. for-mo'sus). — This is a beautiful species, which occurs in Texas. The dorsum is a rich dark brown, with a medium elongate white spot near the tip; the sides just behind the legs are also white, and the legs are ringed with white. The length of the body is nearly one third inch. Genus TRACHYRH1NUS (Trach-y-rhi'nus) The inner margin of the patella of the pedipalps is extended at the tip into a spur-like prolongation; the body is very hard and rough; the eye-tubercle is spinose; and the coxae of the third and fourth legs are enlarged in the males. Tracbyrbinus favosus (T. fa-vo'sus). — The body is very hard; the dorsum is nearly square, quite level, has projecting angles on the anterior lateral corners and is coarsely punctate. The colour is grayish, spotted with black, and with a central vase-like mark- ing faintly indicated; the coxae are unicolorous, and the legs mostly black. Occurs in Nebraska and Colorado. 72 Spiders and Their Near Relatives Tracbyrhinus marmoratus (T. mar-mo-ra'tus). — This species was described from New Mexico. It differs from the preceding in having the coxae pale spotted with brown and in having the legs mostly pale. Genus LEURONYCHUS (Leu-ron'y-chus) Similar in most respects to Leiobuniim, but with the palpal claw smooth, and without the lateral rows of teeth on the coxae. Two species have been found in the Far West. Leuronychus pacificus (L. pa-cif'i-cus). — The body is marked with a brown dorsal stripe; the patellae of the legs are brown lined with white. This species occurs in California and in Washington. Leuronychus parvulus (L. par'vu-lus). — This species differs from the preceding in lacking the dorsal stripe and in that the patellae are not lineate. It occurs in Washington. Genus LEIOBUNUM (Lei-o-bu'num) In this genus the cuticula is soft or subcoriaceous. The anterior and lateral borders of the carapace are smooth. The eye-tubercle is relatively small, smooth, or rarely provided with small, slightly distinct tubercles; it is widely separated from the anterior border. The legs are very long and slender; the fourth pair are much shorter than the second pair. The palpal claw is denticulate. The genus Leiobunum is the largest of this order in our fauna, including sixteen species. The males are separated by Banks ('01) as follows: A A distinct spur on the femur of the palpus; dorsumyellowish, without stripe; trochanters concolorous with the coxae. Occurs in the Northern States. Leiobunum calcar \A. Without a spur on the femur of the palpus. B. Palpus, except the tarsus, mostly black. C. Dorsum dark, often with two large pale spots behind; trochanters usually pale. Occurs on the West coast. Leiobunum exilipes CC. Dorsum pale yellowish, no stripe; trochanters and bases of legs black. Occurs in the Eastern States. Leiobunum nigropalpi 73 Spiders and Their Near Relatives BB. Palpus yellowish or brownish. C. Femur, patella, and tibia of the palpus plainly thickened, dorsum with a black stripe, trochanters dark brown. Found in the District of Columbia. Leiobunum crassipalpis CC. Palpal segments not thickened. D. Femur of the palpus very long, curved, extending much above the surface of the cephalothorax, dorsum with a distinct black stripe, trochanters black. A widely distributed species. Leiobunum vittatum DD. Femur of the palpus shorter, dorsum without a distinct black stripe. E. Dorsum dark, with two large yellowish spots on the union of the cephalothorax and abdomen. Occurs in California. Leiobunum bimacuJatum EE. Not so marked. F. Apex of the tibia of the second pair of legs white, trochanters black, body short. Occurs in the Eastern States. Leiobunum longipes FF. Apex of the second tibia not white. G. Apex of the femur of the first pair of legs white preceded by a black band, coxae pale out- side. Occurs in New Mexico and in Texas. Leiobunum townsendi GG. First femur not so marked. H. Trochanters dark, contrasted in colour with the coxae. 1. Legs black, dorsum dark brown, eye- tubercle slightly spinulate. Occurs in Ohio. Leiobunum nigripes II. Legs pale, sometimes marked with black. J. First femur barely as long as the body, tips of femora and tibiae dark brown or black, eye-tubercle nearly smooth. Occurs in the Eastern States Leiobunum formosum JJ. First femur plainly longer than the body, eye-tubercle spinulate, legs not so dis- tinctly marked with black. 74 Spiders and Their Near Relatives K. Abdomen tapering behind, dorsum golden, base of femora not black, trochanters dark brown, species of moderate size. Occurs in New York. Leiobunum verrucosum KK. Abdomen rather short and broad, legs very long, small species. L. Dorsum and trochanters light brown, bases of femora not black. Occurs in the Southern States. Leiobunum bicolor LL. Dorsum yellowish, trochanters and bases of femora black. Occurs in Alabama. Leiobunum speciosum HI I. Trochanters pale, concolorous with the coxae. 1. Body short and broad, femur of the last pair of legs often black at base, small species. Occurs in the Eastern States. Leiobunum politum II. Body tapering behind, femur of the fourth legs not black at base, larger species. J . Extremely spinose beneath, an impressed line on the last ventral segment, large species. Occurs in the Southern States. Leiobunum flavum J J. Moderately spinose, rather granulate, no impressed line, species of moderate size. Occurs in the Eastern States. Leiobunum ventricosum Genus HADROBUNUS (Had-ro-bu'nus) The body is large; the legs are moderately slender, the femur of the first legs is much shorter than the body, in the female shorter than the width of the body, there are several false articula- tions in the metatarsus of the first legs; the eyes are of normal size, the eye-tubercle is of moderate size and with a few denticles above; there are no spines on the anterior margin of the cephalothorax; the pedipalps are without spines, and with the last segment 75 Spiders and Their Near Relatives longer than the penultimate, the palpal claw is dentate. Two species have been described. Hadrobunus grandis (H. gran'dis). — In this species the dorsum is finely spinulate; the legs are longer than in the following species, and in the female are not much marked with brown at the tips of the segments. It occurs in the Eastern States. Hadrobunus maculosus (H. mac-u-lo'sus). — This species occurs in the Southern States and differs from the preceding in that the dorsum is more smooth and is marked with many small, round, pale spots; the legs are shorter and are more marked with brown. Genus MESOSOMA (Mes-o-so'ma) This genus differs from Leiobunum in that the body is very hard and granulate both above and below; the legs are very short; and the fourth pair of legs are nearly as long as the second pair. Mesosoma nigrum (M. ni'grum). — The body is ovate; it is black above, light beneath, the legs are black except at the base; the ocular tubercle is destitute of spines but is armed with obtuse granules. Length of body about one fifth inch. This species occurs in the Southern and Western States. Family ISCHYROPSALIDiE (Isch-y-rop-sal'i-dse) This family differs from the Phalangiida?, to which it is allied, in the following characteristics: the last segment of the pedipalps is shorter than the penultimate one and is clawless; the coxa of the fourth leg is not fused with the adjacent sternite of the abdomen; the endite of the second leg is directed vertically downward; and there are no tibial spiracles. Only one genus of this family has been found in the United States. Genus TARACUS (Tar'a-cus) The members of this genus can be separated at a glance from all other harvestmen occurring in our fauna by the great length of the chelicerae, which are longer than the body and project forward (Fig. 58). Three species have been found in the Far West. Taracus spinosus (T. spi-no'sus). — This species differs from the other two in that the dorsum of the abdomen is spinose, and 76 Spiders and Their Near Relatives the chelicerae are pale in colour. It measures about one twelfth inch in length. The colour is pale yellowish with the claws of the chelicerae reddish brown. It was found in California. Taracus pallipes (T. pal'li-pes). — In this and in the following species the dorsum of the abdomen is smooth and the chelicerae are dark. In this species the chelicerae are smooth. The cephalo- thorax is pale, with a broad, black, median stripe, as wide as the base of the chelicerae; the abdomen is dark gray above with black spots; the venter is pale, darker near the tip. The length of the body is one fourth inch; the chelicerae are one half longer. This species occurs on the Pacific Coast; it was described from the State of Washington. Fig. s8. taracus packardi Taracus packardi (T. pac-kar'di). — The dorsum of the abdomen is smooth and the chelicerae are dark, as in the preceding species. But the chelicerae are rough and armed with very distinct spines on the basal segment. The length of the body is one fifth inch. This species has been found in. Colorado and in New Mexico (Fig. 58). Family NEMASTOMATID/E (Ne-mas-to-mat'i-dae) In the Nemastomatidae the sternites of the abdomen are free, overlapping, and without a median divisional sulcus; the first and second abdominal sternites are narrowed anteriorly and coni- cally produced between the coxae, and only overlapping the posterior two pairs to a relatively small extent; and the eighth or penultimate tergite is large and greatly expanded laterally. Only two genera of this family have been found in the United States; these can be separated as follows: A. Fourth segment of the palpus much thickened. P. 77. Phlegmacera AA. Fourth segment of the palpus scarcely thickened. P. 78. Nemastoma Genus PHLEGMACERA (Phleg-mac'e-ra) In this genus the fourth segment of the palpus is much thickened. Three species h:.ve been described. 77 Spiders and Their Near Relatives Phlegmacera bryantii (bry-an'ti-i). — -This species differs from the two following in the presence of several false articulations in the femora of the third and fourth pairs of legs. The eye tubercle is very broad. This is an Alaskan species; it was found on the snows of Mount St. Elias. Phlegmacera occidentale (P. oc-ci-den-ta'le). — -There are no false articulations in the femora, as in the preceding species. The basal segment of the abdomen bears a row of spines, the median pair of these is much the largest; the next four segments have each a pair of humps crowned with stiff hairs. The colour of the body is pale, with a large brown spot on the cephalothorax; the eye-tubercle is black; and there is also a large brown spot on the front part of the dorsum of the abdomen. Length of body one tenth inch. Occurs in Washington State. Phlegmacera cavicolens (P. ca-vic'o-lens). — This species agrees with the preceding in lacking false articulations in the femora, but differs from it in lacking also the pair of prominent erect spines on the anterior part of the abdomen. It is found in caves and in other dark situations. It is widely distributed in the East. Genus NEMASTOMA (Ne-mas'to-ma) This genus differs from the preceding in that the fourth segment of the palpus is scarcely thickened. Four species are known. Nemastoma inops (N. i'nops). - -This differs from the two following species in that the fourth segment of the palpus is less than twice as long as the fifth. It is a cave-inhabiting species found in Kentucky. Nemastoma modestum (N. mo-des'tum).— - The dorsum is granulated and armed with tubercles. Near the union of the cephalothorax and abdomen there are two diverging rows of four curved spines. The species has been found in California and in Washington State. Nemastoma troglodytes (N. trog-lo-dy'tes).— - This is a cave- inhabiting species found in Utah. It differs from the preceding in that the dorsum is devoid of spines. Nemastoma dasycnemon (N. das-y-cne'mon). — This is a minute species, the body measuring less than one twenty-fifth of an inch in length. The legs are armed with short, acute, 78 Spiders and Their Near Relatives perpendicular spines and with long, slender hairs, which in their basal half stand at right angles to the leg, and in their distal half are bent forward and are somewhat matted. It has been found in Missouri and in North Carolina. Family TROGULIDiE (Tro-gu'li-dae) The Trogulidas differs from the Nemastomidae, with which it is closely allied, in that the sternites of the abdomen, except the genital and anal, are fused, do not overlap, and are marked by a median longitudinal sulcus; and in that the first and second abdominal sternites are widely rounded anteriorly and overlap considerably the proximal extremities of the two posterior pairs of coxae; and also in having the eighth or penultimate tergite small and narrow, and not expanded laterally. The legs are shorter and stouter than in the preceding family; and the cara- pace bears a frontal process which conceals the cheliceras and pedipalps. This family is represented in our fauna by only two genera, both of which are restricted to the Pacific Slope. They are separated as follows by Mr. Banks: A. Eye-tubercle projecting in the form of a spoon, two spines at each side on the anterior margin. P. 79. Ortholasma AA. Eye-tubercle branched, a single club at each side on the anterior margin. P. 80. Dendrolasma Genus ORTHOLASMA (Or-tho-las'ma) The cephalothorax is armed with a pair of spines at each side on the anterior margin. The eye-tubercle projects in front in the form of an almost flat, gradually widening plate; the tip of the eye-tubercle is rounded, with a more dense central rib and some lateral ribs connected by a membrane. The eyes are but partly visible from above. Only two species of these harvestmenare known; both of these are from the Pacific Coast, and were described by Mr. Banks. Ortholasma pictipcs (O. pic'ti-pes). — The form of the body of this remarkable harvestman is represented by Fig. 59; the legs are long and slender, and are not represented in the figure in order 79 Spiders and Their Near Relatives to save space. The forward projecting process of the eye-tubercle has only four or five openings on each side; and the ribs of this process project beyond its edge. This species was discovered in California by Dr. J. C. Bradley. Ortholasma rugosa (O. ru-go'sa).— - This species differs from the preceding in having six or more openings on each side of the Fig. 59- ORTHOLASMA PICTIPES forward projecting process of the eye-tubercle; and in that the femora and tibue of the legs are not banded. The colour of mature individuals is black, of young ones brownish. The length of the body is about one seventh inch. This species is common in southern California. Genus DENDROLASMA (Den-dro-las'ma) The cephalothorax is armed with a club at each side on the anterior margin. The eye-tubercle projects forward in the form of a central support, with lateral branches somewhat connected 80 Spiders and Their Near Relatives at the tips, the whole forming an oval figure. The eyes are visible from above. Dcndrolasma mirabilis (D. mi-rab'i-lis). — The colour of the body is brown or black with the venter paler; the projecting part of the eye-tubercle and the club at each side are whitish. The sides and the hind margin of the cephalothorax are armed with a row of tubercles which are more or less connected, and there is a square of similar tubercles just behind the eye- tubercle. The dorsum of the abdomen has also many series of tubercles. The length of the body is one eighth inch. This species was discovered in Washington State and is the only known one of the genus. Order ACARINA (Ac-a-ri'na) The Mites In this order the abdomen is unsegmented and is not con- stricted at the base, but is broadly joined to the cephalothorax, v^Y^M2 Fig. 60. THE [TCH-MITE a, from below b, from above with little or no indication of a division between these two regions. The result of this is that the entire body often presents a more or less sac-like appearance. (Fig. 60.) In many members of the order, however, the body is divided into two regions which are commonly termed the cephalothorax and the abdomen (Fig. 61). But these regions do not correspond to those bearing the same names in the other orders of the 8j Fig. 61. BDELLA PEREGRTNA (after Banks) Spiders and Their Near Relatives Arachnida. The so-called abdomen of mites includes the true abdomen and the last two thoracic segments; this is indicated by the fact that it bears the third and fourth pairs of legs. In many mites the body is marked by numerous transverse, fine lines, which are so impressed as to appear like the divisions between minute segments, but the number of these divisions on the ventral aspect of the body may differ greatly from that of the dorsal. Normally there are six pairs of appendages, as with other arachnids; these are the chelicerae, the pedipalps, and four pairs of legs. As a rule the chelicerae consist of two segments and are often chelate. In many forms, however, the chelicerae are slender, Fig. 62. SEVERAL TYPES OF PEDIPALPS a, Bdella b, Cheylctus c, Arrenurus d, Trombidium (adapted from Banks) needle-like, and fitted for piercing. This difference in form of the chelicerae is not of great taxonomic value, as in several cases the two types exist within the same family. The pedipalps consist of not more than five segments; the\ may be prominent or greatly reduced in size. They vary greatly in form and in function. In some mites, they are simple, filiform, and have a tactile function; in others they are specialized fo; predatory purposes, being armed with spines, hooks, or claws; and in still others they are chelate, the chela being used for clinging to some object. In some forms, more or less distinct endites are present. In the harvest-mites, and in some other families, the next to the last segment of the pedipalp is armed with one or two 82 Spiders and Their Near Relatives claws, and the last segment is often clavate and appears like an appendage of the preceding segment, in such cases it is termed the thumb. Several types of pedipalps are represented in Fig. 62. The head segments, those bearing the chelicerae and the pedipalps, are often more or less distinct from the following thoracic segment, and form what has been termed the beak, rostrum, or capitulum (ca-pit'u-lum); this division, however, is indistinct in some forms; and sometimes the beak is partly or completely retracted into the following segments. When the beak is thus retracted, the opening of the body from which the mouth-parts project is known as the camerostoma (cam-e-ros'to- ma). In Uropoda the base of the first pair of legs is also retracted into the camerostoma (Fig. 63). Sometimes the basal segments of the pedipalps are united and form a Up, or labium; and above the chelicerse there is in many forms a thin corneous plate, termed the epistoma (e-pis'to-ma). The sides of the epistoma may be united to the labium and thus form what is known as the oral tube, for it is through it that the chelicerae are protruded. In several families there is an organ termed the tongue or hypostoma (hy-pos'to-ma), which arises from the inner base of the beak, and may be VvA- 6i- ..... . . , . .... UROPODA. VENTRAL ASPECT divided or simple. In the ticks it is (after Banks) large and roughened with sharp teeth. Sometimes the hypostoma has a groove above, called the vomer. As in other arachnids, the normal number of legs is four pairs; but almost invariably the newly hatched young has only three pairs, and in the family Eriophyidae even the adults have only two pairs. In the remarkable genus Ptcroptus, which is parasitic on bats, the larval stage is passed within the body of the mother, and the young mite when born has four pairs of legs. That the possession of only three pairs of legs by larval mites is an adaptive characteristic is shown by the fact that the embryo of certain forms, as Gamasus and Ixodes,, has four pairs of legs, one pair of which is aborted before the birth of the larva, and is again developed when the larva transforms to a nymph. 83 Spiders and Their Near Relatives The legs consist of from five to seven segments. When only five segments are present they are the coxa, trochanter, femur, tibia, and tarsus; the tibia may be divided forming a patella, and sometimes the femur is also divided. In some forms the terminal segments of the legs are divided by more or less distinct false articulations. The tarsus ends in one or two claws; and in many cases an empodium is present; this may be either a cup-shaped sucker or may be claw-like. One or more pairs of lateral eyes are usually present; as a rule these are sessile, but sometimes they are elevated on pedicels. Rarely the eyes are situated near the middle line of the body. There is great difference in the position of the openings of the abdomen. Normally the genital aperture is on the ventral surface of the abdomen near the base; but in some forms, as the ticks, the genital segment is pushed forward between the legs so far that it is close to the mouth; and in other forms the genital opening is at the extreme tip of the body, and the anus is upon the dorsal aspect of the abdomen. Mites breathe either by tubular tracheae or by the general surface of the body. In those forms that possess tracheae there are great differences as to the position of the spiracles; these variations have been used by some writers in limiting the principal divisions of the order. In the course of their postembryonic development, mites undergo a metamorphosis. Most species are oviparous, some are ovoviparous and a few are viviparous. From the egg there appears a form which normally has only three pairs of legs; this is known as the larva. The use of the term larva in this con- nection is appropriate; for this form resembles the larva of an insect with a complete metamorphoses in being adaptive, as is shown by the temporary reduction of the number of legs. The larva feeds for a time and then, after a resting stage, the skin is shed and the eight-legged nymph appears. Usually at least, the added pair of legs is the fourth. There may be one or more nymphal moults, and the successive instars may differ in appear- ance, but all lack a completely developed genital orifice. At the close of the nymphal life there is a resting stage during which the nymph transforms to the adult, there being a histolysis and a rebuilding of some of the internal organs as in the pupae of insects. Variations from this usual course of transformation occur. 84 Spiders and Their Near Relatives Thus in the genus Pteroptus the larval stadium is passed within the body of the mother, and in the genus Pediculoides the young are retained within the body of the mother till they reach the adult stage. And in many there has been developed a peculiar nymphal instar, known as the bypopus (hyp'o-pus), the function of which is the distribution of the species. The hypopus differs greatly in structure from the preceding and the succeeding nymphal instars, both of which have normal legs and mouth- parts. In the hypopus there is no mouth opening and no mouth- parts; and the legs are short and not fitted for walking. On the ventral surface near the tip of the abdomen there is an area pro- vided with several sucking disks by means of which the hypopus attaches itself to an insect or other animal and is transported to some other locality, where it may find a suitable breeding place. When this is reached the hypopus transforms into a normal nymph. The order Acarina is one of great biologic interest and of equally great economic importance; but the minute size of most of the species makes its study somewhat difficult, and compara- tively few students are attracted to it. In fact few people realize the immense number of individuals and of species of mites that are about us. In a recent catalogue. Banks ('07) enumerates 450 species, representing [33 genera, that are found within the United States. And it is probable that not more than one third of our species have been described. It is impractical to treat the Acarina in this work as fullv as are treated the other orders of Arachnida, without greatly exceeding the desirable limits of space. The student who wishes to study this group seriously must make use of more special works. Fortunately a most excellent treatise on the mites of this country has been published by Banks ('04) who has given much attention to the order and who has described many of our known species. In the preparation of the account given here, I have freely used this work by Banks. Among other important American papers is a Review of the Genera of the Water-mites, by Wolcotl ('05); a Revision of the Ixodoidea, or Ticks of the United Slates, by Banks ('08), papers on the Oribatoidea by II. E. F.wing, and studies on the gall-mites are being published by Parrott, Hodgkiss, and Schoene at the Geneva, N. Y., Experiment Station. I here are many European works on this order; the most important is Canestrini's Prospctto dell' Acarofauna Italiana, published at 85 Spiders and Their Near Relatives Padua, in parts, which appeared in the years 1885 to 1899. An older standard work is that of Megnin, Les Parasites et les Maladies Parasitaires, Paris, 1880. Twenty-two of the families of mites are known to be rep- resented in our fauna.* These twenty-two families are grouped into eight superfamilies. We have space here for only a brief discussion of the superfamilies. The eight superfamilies are separated by Banks as follows: A. Abdomen annulate, prolonged behind; very minute forms; many with but four legs. P. 93. Demodicoidea AA. Abdomen not annulate nor prolonged behind; all with eight legs in the adult state. B. With a distinct spiracle upon a stigmal plate on each side of the body, usually below, above the third or fourth coxae or a little behind; palpi free; skin often cori- aceous or leathery; tarsi often with a sucker. C. Hypostome large, furnished below with many recurved teeth; venter with furrows; skin leathery; large forms, usually parasitic. P. 89. Ixodoidea CC. Hypostome small, without teeth; venter without fur- rows; body often with coriaceous shields, posterior margin never crenulate; no eyes. P. 90 Gamasoidea BB. No such distinct spiracle in a stigmal plate on this part of the body. C. Body usually coriaceous, with few hairs ; with a specialized seta arising from a pore near each posterior corner of the cephalothorax; no eyes; mouth-parts and palpi very small; ventral openings of the abdomen large; never parasitic; tarsi never with a sucker. P. 91. Oribatoidea CC. Body softer, without such specialized seta. D. Living in water. P. 88. Hydrachnoidea DD. Not living in water. E. Palpi small, three-jointed, adhering for some distance to the lip; ventral suckers at genital opening or near anal opening usually present; no eyes; tarsi often end in suckers; beneath the * In Banks' Treatise twenty-five families are described; but in his later catalogue three of these families are united with other families. 86 Spiders and Their Near Relatives skin on the venter are seen rod-like epimera that support the legs; body often entire; adult fre- quently parasitic. P. 92 Sarcoptoidea EE. Palpi usually of four or five joints, free; rarely with ventral suckers near genital or anal open- ings; eyes often present; tarsi never end in suckers; body usually divided into cephalothorax and abdomen; rod-like epimera rarely visible; adults rarely parasitic. F. Last segment of palpi never forms a "thumb" to the preceding joint; pal-pi simple, or rarely formed to hold prey; body with but few hairs. P. 87. Eupodoidea FF. Last segment of palpi forms a "thumb" to the preceding, which ends in a claw (a few excep- tions); body often with many hairs. P 87. Trombidoidea Superfamily EUPODOIDEA (Eu-po-doi'de-a) The Eupodoidea includes two families, the Eupodidae and the Bdellidas, each of which contains only a small number of known American species. These are predaceous mites which feed on small insects or insect eggs. They live as a rule in moist places, in moss, among fallen leaves, on rotten bark, and in other similar situations; but some are found on the leaves of trees. Many of the species are red or marked with this colour. But our most conspicuous red mites do not belong here; these are the harvest-mites described later. Superfamily TROMBIDOIDEA (Trom-bi-doi'da-e) The Red-spiders and the Harvest-mites The Trombidoidea includes six families, two of which are of general interest. These are the Tetranychidas or "red-spiders" and the Trombidiidae or harvest-mites. The Tetranychidae ( 1 et-ra-nych'i-da?) are of considerable economic importance on account of their injuries to cultivated plants. They are well-known under the common name "red- spider." In the colder portions of the country they are common 87 Spiders and Their Near Relatives pests in greenhouses and in the warmer and drier regions they often infest fruit trees in the open air to a serious extent. The common species of the greenhouse is Teiranychus telarius (T. te-la'ri-us). To this family belongs also the clover mite, Bryobia pratensis (Bry-o'bi-a pra-ten'sis), which infests clover and other annual plants as well as fruit trees. The species that infest greenhouses can be kept in check by keeping the plants moist, spraying them every day. But the best remedy is flowers of sulphur applied either as a dry powder or as a spray. A spray of kerosene emulsion is also effective, killing the eggs as well as the mites. The family Trombidiidae (Trom-bi-di'-i-dae) includes the well- known harvest-mites. These are always red in colour, but some are much darker than others. Most of the species are of moderate or large size. A common species in the Eastern States, Trom- bidium sericeum (Trom-bid'i-um se-ric'e-um — ) is found in moist woodlands and often attracts attention by its bright red colour and silky vestiture. In the harvest-mites the body is divided into two regions, the cephalothorax and abdomen; but the so-called abdomen bears the third and fourth pairs of legs. The body and legs are covered either with bristles or with feathered hairs. There are two pairs of lateral eyes; in many cases these are borne on pedicels. The six-legged larvae of some species are the "red-bugs" of the Southern States that attach themselves to man, and cause serious annoyance. They burrow beneath the skin and produce inflamed spots. They can be killed by the use of a sulphur oint- ment. The mature mite is not parasitic, but wanders about feeding on small insects. Superfamily HYDRACHNOIDEA (Hy-drach-noi'de-a) The IVater-rnites The Hydrachnoidea includes two families, the Hydrachnidas and the Halacaridae. The Halacaridae (Hal-a-car'i-dae) is a small family of marine mites. The species that occur along the coasts of North America have not been studied, only a single species having been described; but of the Hydrachnidae about one hundred North American species are known. These represent twenty-five genera. 88 Spiders and Their Near Relatives In the Hydrachnidae (Hy-drach'ni-dae) the body is short, usu- ally high, and sometimes nearly spherical. There is no division between the cephalothorax and abdomen. They have one or two pairs of eyes, which in some cases are situated near the median line. In most species the adult mite lives free in the water, but some are parasitic in the gills of mollusks. Nearly all of the species live in fresh water; but some are found in brackish water, and a few live in the littoral zone of the sea. The free species feed on small Crustacea, infusoria, and minute insect larvae. The larval mites are often found attached to aquatic insects; they appear like club-shaped eggs attached by the small end. Superfamily IXODOIDEA (Ix-o-doi'de-a) The Ticks Of all mites, the ticks are the ones that most often attract the attention of those who are not making a study of this order. This is due to the fact that they attach themselves to man and to domestic animals and are exceedingly an- noying pests. This is especially true in the warmer portions of the country. Among the ticks are also the most important members of the order from an economic stand- point as certain species transmit serious diseases. Ticks are parasitic on mam- mals, birds, and reptiles. In most cases they do not seriously injure their host, but in others they cause serious inflammation and swelling of the infested part. Among those that transmit diseases the Southern cattle tick is the most important one that occurs in this country. It is the Southern cattle-tick, Boophilus annulatus (Bo- oph'i-lus an-nu-la'tus) (Fig. 64) that transmits the tick-fever, 8q Fig. 64. THE CATTLE TICK a, female b, male Spiders and Their Near Relatives or Texas-fever as it was formerly called, from one animal to another. This disease has caused the death of thousands of cattle in this country; and makes it extremely difficult to introduce cattle from the North into the South. This tick is found only in the South and the Federal Government has established a quarantine line across which cattle are not allowed to be shipped or driven without being freed from the ticks. The Department of Agriculture at Washington and several of the Southern Experiment Stations have issued publications giving the life history of this tick in great detail and suggestions as to methods of preventing the spread of the disease; these can be obtained on request by any one interested in the subject. In some of these publications this tick is designated as Margaro- pus annulatus (Mar-gar'o-pus an-nu-la'tus). The cause of the disease is a protozoan parasite Babesia bovis (Ba-be'si-a bo'vis), which lives in the blood of cattle, destroy- ing the red blood corpuscles and which is transferred from one animal to another by the tick. Even the young of ticks that have infested diseased cattle may transmit the disease. Superfamily GAMASOIDEA (Gam-a-soi'de-a) The Gamasid Mites The Gamasid mites are often observed attached to beetles and other terrestrial insects upon which they spend a part of their life. It was formerly believed that these mites were para- sites of the insects, but it has been found that they are nymphs which secure transportation in this way, a method of distribution of the species. A few species are parasitic on birds, bats, and small mammals; some are found in ant-nests; a great many occur among fallen leaves, and some live in decaying substances, either animal or vegetable. Most species prey on small insects or on other mites. Among those found on insects, some are attached by an anal pedicel formed of excretions. Among the species that are parasitic on birds there is one Dermanyssus gallince (Der-ma-nys'sus gal-li'nae), which is a serious pest of poultry. The mites of this species hide in cracks and crevices by day, but at night crowd upon the fowls and suck 90 Spiders and Their Near Relatives their blood. This pest can be destroyed by spraying the poultry houses with kerosene. All of our species are now included in the family Gamasidae of which nearly fifty species have been described representing eighteen genera. Superfamily ORIBATOIDEA (Or-i-ba-toi'de-a) The Oribatid Mites The oribatid mites are now classed as a single family, the Oribatidae; this is a large one, nearly one hundred and fifty species being known from North America alone. Nearly all of these were described by either Mr. Banks or Mr. Ewing; the number of species will doubtless be greatly increased when our fauna is more thoroughly explored. In most cases these mites are distinguished by the presence of a pair of large club-shaped setae arising from near the pos- terior corners of the cephalothorax (Fig. 65). These setae are known as the pseudo-stigmatic organs, from the fact that the trichopores from which they arise were formerly believed to be spiracles. With most of the Oribatidae thecuticula is coriaceous, giving the . . . Fig. 65. AX ORIBATID MITE mites some resemblance in appear- {Hopiodema sphmda) tafter Banks) ance to small beetles. For this reason they are sometimes termed "beetle mites"; but as this name is often applied to those gamasid mites that are found on beetles it is not distinctive. The resemblance of the oribatid mites to beetles is increased by the fact that the suture separating the cephalothorax and abdomen is usually quite distinct. Many of the common forms are shining black in colour. These mites are of little or no economic importance; some of them are supposed to injure grass to a slight extent; but most of them are found among moss, on the bark of trees, and on the ground under wood, bark, stones, and fallen leaves. .Most of the species feed on vegetable matter, a few are found on decaying animal matter, and some bore into decaying wood. 91 Spiders and Their Near Relatives Superfamily SARCOPTOIDEA (Sar-cop-toi'de-a) The Itch-mites and Others The Sarcoptoidea include seven families of mites; but several of these families are small and include only forms that are not likely to attract the attention of the ordinary observer. Some of these forms, however, are of great scientific interest, as for example Pediculoides, which lives parasitically upon insects, and which gives birth to sexually mature young. 1 1 is in one of the families of this group, the Tyroglyphidae, that those mites that have the remarkable migratory stage, the hypopus, described on an earlier page, are found. It is to this family also that belong certain species which attack food products as cheese, sugar, flour and dried meats; these are often of considerable economic impor- tance. The disease iV J/ 1 /a known as " grocers' itch" is caused by these mites which sometimes spread from infested ma- terials to the hands of those handling them. To the family Sarcoptidae belong the itch-mites, which are so-called because they often burrow within the skin of man, causing the disease known as the itch. The diseases of domestic animals known as scabies or mange are also due to members of this family. The species attacking man is Sarcoptes scahei (Sar-cop'tes sca'be-i) (Fig. 66). It is apt to infest the soft skin between the fingers and may spread to other parts of the body. The mites make burrows within the skin and the eggs are deposited within the burrows. The spread of the disease is due to the spreading of the mites from one person to another; this is often brought about by hand-shaking. The remedy most often used is a sulphur ointment, by means of which the mites can be killed. The disease known as sheep-scab is caused by the mite Fig. 66. SCARCOPTES SCABEI 92 Spiders and Their Near Relative: Sarcoptes ovis. This disease is combatted by dipping the sheep in some poisonous solution. A "sheep-dip" approved by the Federal Government is made of extract of tobacco or nicotine solution and flowers of sulphur. It contains five hundredths of one per cent, of nicotine and two per cent, flowers of sulphur; or, for the first dipping in lieu of the sulphur, more nicotine is used so that the solution contains not less than seven hundredths of one per cent, of nicotine. A second dipping of the infested animal should be made six or eight days after the first, in order to kill the mites that have hatched in the interval. Superfamily DEMODICOIDEA (De-mod-i-coi'-de-a) The Gall-mites and Others In this superfamily are grouped certain very minute mites that agree in having the abdomen annulate and prolonged behind; it includes two families. The more important of these two families is the Eriophyidaeor gall-mites. The members of this family have only four legs and these are five-jointed. The mites live on plants and often within galls. Some species produce galls which resemble those made by plant liceoraphids in having an open mouth. These galls may g be trumpet-shaped or they may be but slightly elevated resembling a blister. A common disease of the pear and apple, known as the pear-leaf blister, is produced by Eriophyes pyri (Er-i-o- phv'es py'ri) (Fig. 67). The blisters characteristic of the disease are swellings of the leaf, within which there is a cavity affording a residence for the mites. Figure 68 represents a section of a leaf through one of these galls. Here the leaf is seen to be greatly thickened at the diseased part. On the lower side there is an opening through 93 Fig. 67. ERIOPHYES PYRI O Fig. 68. DIAGRAM OF GALL OF ERIOPHYES'PYRI g, gall n,n. normal structure of leaf 0, opening of gall «, eggs (after Soraur) Spiders and Their Near Relatives which the mite that started the gall entered, and from which young mites developed in the gall can escape, in order to start new galls. In addition to the swelling of both surfaces of the leaf its internal structure is seen to be modified. In some parts there is a great multiplication of the cells, and in others a large part Fig. 69. GALL OF ERIOPHYES PYRI g, gall n,n, uninjured part of leaf 0, opening of gall of the cells have been destroyed. Two eggs of mites are rep- resented in this gall. As the season advances, and the galls become dry and brownish or black, the thicken- ing of the leaf becomes less marked. In fact, in some cases there is a shrinkage of the parts affected. Figure 69 represents a section through a leaf collected and studied in October. The most conspicuous of the abnormal growths on leaves caused by mites are bright coloured patches, often mistaken for fungoid growths; these occur on the leaves of various trees, and are due to an abnormal development of the epidermal plant cells or a deformation of the plant hairs, caused by the mites. This type of abnormal growth is termed an erineum (e-rin'e-um). The members of the family Demodecidae resemble the gall-mites in having the body annulate and prolonged behind; but differ in having eight legs which are three-jointed. It includes a single genus, Demodex, the species of which are found in the sebaceous glands and hair-follicles of various mammals. The species that infests man is Demodex folliculorum (Dem'o-dex fol-lic-u-lo'rum) (Fig. 70). It was formerly sup- posed to be the cause of "blackheads" or comedones (com-e- do'nes) on the face; but it has been found that the mites occur in healthy as well as diseased follicles. Fig. 70. DEMODEX FOLLICULORUM (after Megnin) 94 CHAPTER II: THE EXTERNAL ANATOMY OF SPIDERS Spiders resemble the allied animals described in the preceding pages in having the segments of the body grouped in two regions, the cephalothorax (ceph-a-lo-tho'rax) and the abdomen (Fig. 71), in having four pairs of legs fitted for walking, and in having the antenna? modified into organs of prehension, the chelicera:. The spiders differ from other Arachnida in having the ab- domen unsegmented and joined to the cephalothorax by a narrow stalk. There is a single small family of spiders, Liphistiidtv, in which the abdomen is segmented; but representatives of this family have been found only in the East Indies. In the genus Tetrablemma, found in Ceylon, the abdomen bears a series of plates, which are evidently vestiges of a segmented condition. But in all American spiders the abdomen is sac-like. THE CEPHALOTHORAX In spiders the cephalothorax, like the abdomen, is unseg- mented; although frequently the head and the thorax are slightly separated by a furrow, the cervical groove (Fig. 72). In such cases, most writers refer to the head as the cephalic part, or the pars cephalica, and to the thorax as the thoracic part, or the pars thoracica; but the simple terms head and thorax are sufficient for all purposes, and will be used in this book when it is necessary to refer to the principal divisions of the cephalothorax. The hard integument forming the dorsal wall of the cephalothorax is termed the carapace (car'a-pace). THE HEAD The head is that portion of the cephalothorax which bears the eyes and the so-called mouth-parts, the appendages that are used for seizing and chewing their prey. It is either slightly or not at all separated from the thorax; but it is almost always 95 The External Anatomy of Spiders easily distinguished. It is usually wedge-shaped behind; the lateral portions of the thorax extending a considerable distance on each side of it (Fig. 72). The Eyes.— The eyes are all simple, resembling in appear- ance the ocelli or simple eyes of insects; in none of them is the Fig. 71. A SPIDER. SHOWING THE DIVISION OF THE BODY INTO CEPHALOTHORAX AND ABDOMEN outer layer divided into facets as in the compound eyes of insecb. They are usually situated near the front end of the head; in some cases they are grouped upon a tubercle (Fig. 72); in others, they are separated so as to occupy nearly the whole width of the head (Fig. 73).* The normal number of the eyes is eight; but two, four or six of them may be wanting and certain cave spiders are blind. The number and the arrangement of the eyes furnish characters which are much used in classification, as is shown in later portions of this book. In works on the classification of spiders, two types of eyes are distinguished, the nocturnal eyes and the diurnal eyes. The so-called nocturnal eyes are found in spiders that live in the dark or that frequent shady places; they are distinguished by being pearly white in colour. The so-called diurnal eyes lack the pearly lustre and are variously coloured. This distinction * See page ioon the primitive position of the eyes. 96 The External Anatomy of Spiders is not a good one; it is discussed at length in the next chapter, where the structure of nocturnal eyes is explained. The anterior median eyes differ from the other six eyes in a remarkable manner as regards their intimate structure and mode of development. These eyes have been termed the postbacillar (post-bac'il-lar) eyes; and the other six eyes, the prebacillar eyes. The differences in structure between these two types of eyes are discussed in the next chapter. In many spiders the eyes are arranged in two transverse rows each containing four eyes (Fig. 73); and this is regarded as the normal arrangement. Special names are applied to the different eyes, the names being suggested by their relative po- sitions when thus arranged. The names are anterior median, applied to the two intermediate eyes of the first row; posterior median, the two intermediate eyes of the second row; anterior Qh- Fig. 72. CARAPACE 01 \ I \K \\ TULA eg, cervical r], radial furrows FiR. 73. MODELOFTHE CARAPACE O] \ SPID1 R \ :! V. i I) FROM \B0\ E. THE W rERIOR Row OF EYES AP- PEARS TO BE PRO( I R\ l D lateral, one at each end of the first row: and posterior lateral, one at each end of the second row. Some writers refer to the lateral eyes as the side eyes. The rows of eyes are frequently curved. When the lateral eyes of a row are farther forward than the median eyes the row <)7 The External Anatomy of Spiders <*>*— O^ Fig. 74- THE MODEL REPRESENTED IN FIG. 73 VIEWED FROM IN FRONT; THE ANTERIOR ROW OF EYES IS RECURVED is said to be procurved; when the lateral are farther back than the median eyes the row is recurved. In determining whether a row of eyes is procurved or recurved, a line passing through the centre of the eyes is considered, and not one tangent to either anterior or posterior border of them, and in case of the anterior row they should be viewed from in front. In this case if the an- terior lateral eyes are higher than the anterior median — i. e., farther from the edge of the clypeus — the row is recurved, although when seen from above the lateral eyes may be farther forward than the median eyes and con- sequently the row is apparently pro- curved. This is illustrated by the accompanying two views of a model (Fig. 73 and Fig. 74). Sometimes the curvature is very great, and the posterior median eyes are widely separated; then the eyes are said to be arranged in three rows (Fig. 75); and in some cases the eyes are in four rows, each pair of median eyes and each pair of lateral eyes constituting a row (Fig. 76). The Areas of the Head. — Special names are applied to different areas of the head; but the areas thus designated are not limited by sutures and consequently the names applied to them do not have the definite morpho- logical significance that similar names have in de- scriptions of insects. The areas most commonly recognized are the following: The eye-space. — That part of the head which is between the rows of eyes is termed the eye-space. The median ocular area. — The space limited by the four median eyes and including that occupied by these eyes is termed the median ocular area. Fig. 75. EYES IN THREE ROWS, LYCOSA CAROLINENSIS Fig. 76. EYES IN FOUR ROWS, LYSSO- MANES C)8 The External Anatomy of Spiders It is also termed by some writers the ocular quadrangle or the ocular quad. In descriptions of the jumping spiders (Attidae), the term ocular quadrangle refers to the space occupied by all of the eyes; and in this book this term is used only in this sense. In the Lycosidae the four posterior eyes outline a trapeziform area, which is described as the quadrangle of the posterior eyes. The ocular tubercle. — In many spiders the eyes are situated on an elevated portion of the head; this portion is termed the ocular tubercle. The clypeus (clyp'e-us). — The space between the eyes and the first pair of appendages, the chelicerae, is termed the clypeus. Frequently, in the tables, reference is made to the width of the clypeus. This is the distance from the front edge of the clypeus to the eyes nearest that edge. The face. — That part of the head which can be seen when the spider is observed from directly in front is termed the face (Fig. 77). This term is used in descriptions of certain spiders belonging to the second suborder. It includes the clypeus and a part or the whole of the eye-space. The front. — The anterior portion of that part of the head lying immediately back of the clypeus is termed the front; the front includes the eye-space, but has no definite limit behind. The Chelicerae (che-lic'e-rae). — The first pair of append- ages of the head are the cbelicercc. They are situated in front of and above the mouth, from which they are separated by the rostrum, and consist each of two segments, a large basal one, and a terminal, claw-like one (Fig. 78). These are the appendages with which the spider seizes and kills its prey. Near the tip of the claw there is the opening of a poison gland (Fig. 79). The chelicerae are modified antennae; the)' are homologous Fir. 7. FACE AND CHELICER/E OF THERIDION Fig. 78. FACE AND CHELICER.E OF ARANEA 99 The External Anatomy of Spiders with the second antennae of Crustacea, but not with the antennae of insects.* It has been supposed by many writers that the chelicerae correspond to the mandibles of insects, and they have, therefore, been called mandibles, a term that cannot properly be applied to them. The term fakes, proposed by Blackwall in 1852, is also used by many writers, but there is no good reason for discarding the much older term chelicerae. The lateral condyle of the chelicera. — In many spiders there is at the base of each chelicera, on the lateral face, a smooth prominence, an articulating condyle (Fig. 80, / c); this may be termed the lateral condyle of the chelicera. This condyle is wanting in many families; and its presence or absence is a useful character in classification. It is sometimes called the basal spot of the chelicera. When the condyle is present, the margin of the clypeus is usually marked with a dark spot at the point of articulation with the condyle. The furrow of the chelicera. — Usually there is a furrow in the basal segment of the chelicera for the reception of the claw when it is closed (Fig. 81); and often there is on one or both sides of this furrow a row of teeth (Fig. 83). In the tarantulas, where the claw moves vertically, the gins of this furrow may be designated as the inner and the outer respectively; in the true spiders, as the upper and the lower. The scopula (scop'u-la). — Frequently there is on the upper side of the furrow of the chelicera, a brush of hairs (Fig. 82, 5); this is the scopula of the chelicera. Scopulae are found also on other appendages. The rake of the chelicera. — In certain tarantulas that burrow in the ground the extremity of the basal segment of the chelicera is armed with several rows of strong teeth, which are used by the spider in excavating its burrow; these constitute the rake of the chelicera (Fig. 83). The claw of the chelicera. — The claw of the chelicera is very hard, curved, and pointed. On its concave face, there are usually • In the Crustacea (lobsters, crabs, and allies) there are two pairs of antenna?, the first antenna or antennules and the second antenna, commonly called the antennae. In spiders the first antenna: are lost, appearing only in the embryo; and the second antenna; are modified into prehensible organs, the chelice.ae. In insects the first antennae are retained and function as feelers, while the second antennae are almost invariably lost: they are retained, however, in a vestigial condition in some Thysanura. IOO Fig. 79- TIP OF CLAW OF CHELICERiE Lc Fig. 83. CHELICERA OF \ TARANTULA SHOWING THE RAKE OF THE CHELICERA Fig. 80. HEAD AND CHELICEK 1; OF A SPIDER lc, lateral condyle Fig. 81. CLAW AND PART OE THE BASAL SEGMENT OF A CHELK ERA a, arlii ul.ir 1 I rite k, toothed keel o, opening of the poi on gland Fig. 84. A CHELATE CHELICERA, PIIOLCUS Fig. 8a. CHELIC1 AGELENA X.EVIA w 1 1 s, scopula k\ OF 11 SCOPULA Fip. 8s. ROSTRUM Wl> ENDITES OJ I 111 PI DD7ALPS OF ARGIOPE, DORSAL \ ll ■ W r, rostrum IOI The External Anatomy of Spiders two delicate keels, of which the lower is usually finely and regu- larly toothed (Fig. 81, k). The claw is traversed by the duct of the poison gland, which opens near the tip of the convex side (Fig. 81, o). The position of this opening is such that it is not closed by the pressure of the claw against the victim, and it allows the venom to flow into the wound made by the claw. The claw of the chelicera is freely movable, but only in one plane. In the tarantulas, the claws of the two chelicerae move parallel to each other in vertical planes; while in the true spiders they move obliquely inward and backward toward each other. The articular sclerite. — At the base of the claw and on the side toward the furrow, there is a small sclerite (Fig. 81, a); this is the articular sclerite of the chelicera. This sclerite may be a vestige of an intermediate segment of the chelicera (See Bernard, '96, p. 322). Chelate chelicerce. — In most cases the chelicera of spiders are of the uncate type (See p. 12); but in a few spiders the terminal portion of the inner margin of the basal segment is prolonged so as to oppose the tip of the claw and thus form a chela (Fig. 84). The Rostrum. — The rostrum or upper lip is a single, median, appendage-like part of the head, which resembles in form and position the labrum of an insect; and it is quite probable that the two are homologous. The rostrum is situated below or behind the chelicerae and between the second pair of appendages, the pedipalps. By removing the chelicerae, the rostrum can be seen lying between and upon the endites of the pedipalps (Fig. 85, r). On the dorsal surface of the rostrum there is a longitudinal, median keel, which is clothed with a band of hairs. The Epipharynx. — On the ventral surface of the rostrum there is a plate which may be termed by analogy the epipharynx. This plate is strongly chitinized, and is marked by many trans- verse striae, which lead to a central longitudinal slit, opening into a longitudinal tube within the rostrum (Fig. 86,. As the tube in the rostrum extends back to the beginning of the oesophagus, the function of these striae in the epipharynx is, evidently, to collect the fluid pressed from the spider's victim and to conduct this fluid to the tube, from which it can flow to the oesophagus. The Labium (la'bi-um).— The ventral wall of the head is 102 Fig. 86. THE EPIPHARYNX OF ARGIOPE a, tip b, basal portion Fig. 88. PEDIPALP OF A TARANTULA EURYPELMA, VENTRAL SURFACE c, coxa /, femur p, patella /, tibia ta, tarsus tr, trochanter Fig. 87. MOUTH-PARTS ^ND STERNUM OF AMAUROBIUS c, cheliccra /, labium P, pedipalp s, sternum Fig. 89. PEDIPALP OF A TRUE SPIDER, TRACHELAS c, coxa en. endite /. femur p. patella sr. SCOpula se. serrula /. tibia td, tarsus Ir, Uochantei !03 The External Anatomy of Spiders formed of a single sclerite, which is usually more or less movable, and which on account of its position has been termed the lower lip or labium. Like the rostrum, the labium is situated between the second pair of appendages, the pedipalps (Fig. 87), the ros- trum occupying a more dorsal position, and the labium, a more ventral one. The labium of a spider is not homologous with the labium of an insect, which is formed of a pair of united appendages. The Mouth. — The mouth cavity is situated between the base of the pedipalps, which form the sides of this cavity. The roof of the mouth is formed by the epipharynx; and the floor by a sclerite, the tip of which lies upon the labium. The mouth is fitted for the reception of only liquid food. The spider cuts and presses its victim; and when it is sucked dry, the hard parts are thrown away. The Pedipalps (ped'i-palps). — The second of the two pairs of appendages of the head are the pedipalps. They are situated one on each side of the mouth; and are more or less leg-like in form, especially in females. By some writers these appendages are termed the maxilla?; but as they are not homologous with the maxillae of insects, this is an undesirable use of the term. Each pedipalp consists of a series of six segments which are named, beginning with the one next to the body: coxa, trochanter, femur, patella, tibia, and tarsus (Fig. 88). These terms are the same as those applied to the corresponding segments of the leg. The pedipalps differ from the legs in that the tarsus consists of a single segment, there being no metatarsus; and there is never more than one tarsal claw, which is wanting in all males and in the females in many genera. A special set of terms for the segments of the pedipalps has been much used and is included here for reference. According to this system the basal part is termed the maxilla and the fol- lowing segments, beginning with the trochanter, are designated as the axillary, humeral, cubital, radial and digital. The endites. — In the tarantulas, except Atypus, the coxa of the pedipalps closely resembles the coxa of a leg (Fig. 88); but in the true spiders the coxa bears a plate, which is the crushing part of the organ, this plate is the endite (Fig. 89, en). On the dorsal surface of the organ there is a suture separating the endite from the basal part of the coxa. This suture is present 104 The External Anatomy of Spiders even in the tarantulas where the endite is but little developed (Fig. 90). The endite is also known as the maxillary plale; but this is an undesirable term, as the pedipalps are not homologous with maxillae. The scopula (scop'u- la). — The internal border of the endite in many cases bears a brush of hairs, this is the scopula of the pedipalp (Fig. 89, sc). The serrula (ser'ru- la). — In addition to the scopula the endite usually bears near its distal margin a keel which is finely toothed, this is the serrula (Fig. 89, se; and Fig. 91). The serrula doubtless plays an important part in lacerating the prey so as to set free the juices upon which the spiders feed. Fig. go. PEDIPALP OF TARANTULA, EURYPELMA; DORSAL SURFACE Fig. 91. THE SERR1 LA OF I Hi: END] II. OF TRACHELAS Fig. 02. PART Ol LEPHTHY- Pll VNTES NEB1 L0S1 5, SHOW l\<; Till I II. I ()X THE (III IK ERA The palpus— -The coxa and the endite taken together are regarded as the trunk of the pedipalp and the remaining seg- ments as an appendage, which is termed the palpus. I(>: The External Anatomy of Spiders In females the tarsus of the palpus resembles the tarsus of a leg except that it consists of a single segment and bears only a single claw or none. But in the males the tarsus of the palpus is more or less enlarged and is very complicated in structure. As the details of this structure vary greatly in different groups of spiders much use is made of them in classification; for this reason a special discussion of this part is given later. The char- acteristic features of the palpi of males are not fully developed until the spider reaches maturity; in young males the palpus appears merely as a simple club-like organ. The Stridulating Organs of the Mouth-parts. — In the sheet-web weavers (Linyphiidos), the external face of the chelicerae is furnished with a file-like series of ridges (Fig. 92) against which the inner face of the femur of the pedipalps is rubbed to produce a sound. And in several genera of tarantulas also the mouth-parts are furnished with stridulating organs. THE PALPI OF MALE SPIDERS INTRODUCTION The remarkable modification of the palpi of the males of spiders into organs for the transference of the seminal fluid to the female at the time of pairing of the sexes attracted the attention of naturalists at a very early date; and the great variety of forms presented by these organs has led systematists to make much use of them in taxonomic work. In practically all of the more important works on the classification of spiders there are figures and descriptions of the palpi of males. Notwithstanding the general recognition of the value of these organs for taxonomic purposes our knowledge of their structure is very inadequate. Several important contributions to this subject have been published and are well-known, notably those of Westring ('61), Menge ('66), Bertkau ('75 and '78), Wagner ('87), Van Hasselt ('89), and Chamberlin ('04 and '08). Still we find, even in the more recent publications, figures of palpi given with almost no effort to identify their parts; and even when some of the parts are named we find different terms applied to homologous parts in the descriptions of different genera. The necessity of selecting, from the many terms that have been proposed for parts of the palpi, a set to be used in this volume and the need of terms for parts that had not been described led me to make a special study of the subject. The results of this study were published recently (Comstock *io); but the more important of them are repeated here so that they may be available for use in this book. THE MORE GENERALIZED TYPES OF PALPI In all spiders the external opening of the reproductive organs of the male is on the lower side of the abdomen near its base, in the epigastric furrow. Some time before pairing the seminal fluid is emitted from this opening and is stored in a tubular cavity in an appendage of the last segment of the palpus, where it is retained until the pairing of the sexes, and from which it then passes to the spermathecae of the female. The transference of the seminal fluid from the opening of the reproductive organs to the receptaculum seminis of the palpus has been observed by several I06 Fig. 93- TARSUS OF FILISTATA HIBERNALIS I, lateral aspect 2, oblique view 3, mesal aspect Fig. 95. PALPUS OF HYI'OCHILUS THOKELLII Fig. 94. DIAGRAM in THE RECEP'l \< 1 I.I M SEMINIS Fig. 96- PALPUS 1 >F LOXOSC1 l 1 - RITES! I \S \7 107 The External Anatomy of Spiders writers. From the published observations it appears that the male spins a delicate web upon which he emits the seminal fluid; after which the fluid is taken up by the palpus. The genital appendage of the palpus of the male is exceedingly complicated in structure in the more specialized spiders, as in the Argiopidae; but it is com- paratively simple in some of the more generalized families. A few illustrations of the simpler forms will be given here. The Filistata Type of Palpus. — in Filistata bibernalis, which is a very common house spider in the South, is found the most simple type of male palpus that I have seen among spiders. In the males of this species, the distal end of the last segment of the palpus, the tarsus, contains a coiled tube (Fig. 93); this is the receptaculum seminis. The proximal portion of this tube is slightly enlarged and ends blindly; the distal part is slender and extends through a slender, twisted prolongation of the tarsus ending at its tip by an open mouth. The modified terminal portion of the tarsus, which contains the receptaculum seminis, is the genital bulb. By looking directly at the tip of the palpus, instead of at one side of it, it can be seen that the base of the bulb is situated in a cavity in the end of the main part of the palpus (Fig. 93, a);* this cavity is the alveolus (Menge '66). The slender prolongation of the bulb, which contains the terminal portion of the receptaculum seminis is the embolus; the embolus is often termed the style. A study of the palpus of Filistata gives a clue to the probable course of the evolution of the genital bulb. It is evident that the bulb is a specialization of the tip of the tarsus, and its most striking feature is the presence within it of the coiled receptaculum seminis. Regarding the origin of the receptaculum seminis, the fact that it is furnished with a transversely striated intima, like the intima of a trachea, indicates that it is merely an invagination of the body-wall. In its primitive form, it was probably a cup-like depression in the tip of the tarsus. In its most perfect form, as seen in the more specialized spiders, the recep- taculum seminis consists of three quite distinct parts: first, the proximal end of it, the fundus, is enlarged so as to form a pouch, the wall of which is more delicate than that of the other parts (Fig. 94, fu.); I have not been able to see taenidia in the intima of this part, and infer that it serves as a compressible bulb; second, the intermediate portion, the reservoir, is a large coiled tube occupying the middle division of the genital bulb (Fig. 94, res.), in this part the taenidia of the intima are well-developed and are sometimes very prominent; third, the terminal portion constitutes the ejaculatory duct, this is a slender tube traversing the apical division of the bulb (Fig. 94, ej. d.) the wall of this duct is often dark in colour, which renders it easy to trace the course of the duct in an expanded bulb. The tracing of the course of the ejaculatory duct is often the only method by which the embolus can be recognized in a complicated palpus; for when the em- bolus is small or when it is lamelliform a slender apophysis may be mistaken for it. After the stage represented by Filistata had been reached, a shifting in the position of the bulb occurred in most spiders. Instead of occupying a terminal position, at the tip of the tarsus, it has moved to one side of the tarsus in all spiders known to me except Filistata. In the tarantulas and in Hypochilus thorellii, the most generalized in many respects of the true spiders, the genital bulb is nearly terminal, but is, nevertheless, distinctly on one side of the tarsus (Fig. 95). In other spiders it has moved to a greater or less extent toward the base of the tarsus, which it has nearly reached in many, as for example in Loxosceles rujescens (Fig. 96)- In Hypochilus (Fig. 95) and in Loxosceles (Fig. 96), the alveolus is compar- atively small; but in many spiders it is large, resulting in the tarsus being more or less cup-like in form; this is shown in some of the figures of the more specialized palpi given later. This cup-like form of the tarsus, as distinguished from its appendage, the genital bulb, suggested for it the name cymbium, which is the classical name of a small drinking vessel. *In the figures of palpi of males given in this chapter, uniform abbreviations are used for the names of the parts. A list of these is given at the close of the account on page 121. 108 The External Anatomy of Spiders The Tarantula Type of Palpus. — In those spiders that are commonly known in this country as tarantulas, and which represent the more generalized of the two principal divisions of the order Araneida, there exists a comparatively simple type of palpus; but in none of them that 1 have seen, or of which 1 have seen figures, is it as generalized as is the palpus of Filistaia. In the palpi of the tarantulas, the genital bulb has migrated to one side of the tarsus; but it is still near the tip of this segment of the palpus (Fig. 97). A striking feature of the bulb is that it is divided into two distinct segments. The smaller basal segment may be termed the basal division of the bulb (Fig. 97, b. d.). The larger segment consists of two parts: a large stout part, which may be termed the middle division of the bulb (Fig. 97, m. d.), and a slender terminal portion, which may be termed the apical division of the bulb (Fig. 97, a. d.) ; there is, however, no distinct line between the middle and the apical divisions, the one gradually merges into the other; but in the more specialized palpi these two divisions are distinctly separated. In the articulating membrane which joins the m. d. Fig. 97. TARSUS OF EURYPELMA Fig. 98. GENITAL BULB OF EURYPELMA CALIFORMCUM bulb to the tarsus, there is on one side a distinct sclerite, which can be seen by removing the bulb from the alveolus (Fig. 98, pet.); this is doubt- less homologous with what has been termed the petiole in more specialized palpi. The greater part of the wall of the bulb in the tarantula type of palpus is very densely chitinized but there is a longitudinal area on the concave side of the middle and apical divisions which is comparatively soft (Fig. 98, p.p.); it may be that this part is distended by blood pressure at the time of pairing as is the ha?ma- todocha in the more specialized palpi; but upon this point I have no data. This soft strip may correspond to that portion of the spiral type of embolus, described later, thai I have designated the pars pendula. I in Palpus of Loxosceles. — In certain genera of the true spiders, the palpi are as simple as in the tarantula type. In Loxosceles of the family Scytodidae, for example (Fig. 96), although the bulb has migrated nearly to the base of the tarsus, the bulb itself is very simple in structure 1 he basal division of the bulb is inconspicuous; the middle division is nearly spherical, and the apical division is long and slender. Here the receptaculum seminis is differentiated into the three parts described above; the reservoir is large, while the ejaculatory duct is very slender. 1 ill. Palpus of Dysdera. — In the family Dysderidae two quite distinct types of palpi occur. In Artadna the palpus resembles very closely thai of Loxo- sceles; but in Dysdera it is of a very different form (Fig. 99); this is due to the Fart that the apical division of the bulb is not slender, and is sharply differentiated from the middle division, its wall being much less densely chitinized. Bui there is on each margin a distinct sclerite; and this part of the bulb bears distinct apoph- yses. At the tip of the apical division there appears to be the beginning ol ! separation into embolus anil conductor. IO9 The External Anatomy of Spiders A summary of the parts of the tarsus in the more generalized types of palpi of males is shown by the following table: Body of tarsus or cymbium, containing the alveolus Genital bulb Internal parts Receptaculum seminis Fundus Reservoir Ejaculatory duct External parts Petiole Basal division Middle division Apical division or embolus THE INTERMEDIATE TYPES OF PALPI There are palpi which hold an inter- mediate position as regards complexity of structure between the comparatively simple tarantula type and the exceedingly complex forms to be described later. These inter- mediate types occur in widely separated portions of the araneid series; but agree in their more essential characteristics; for sake of brevity, I will discuss only a few ex- amples of the intermediate types; and will then pass to a description of forms in which the maximum number of parts are found. The most important characteristic of these intermediate types is that the apical division of the bulb is separated into two, more or less nearly, parallel parts. One of these parts contains the ejaculatory duct of the receptaculum seminis, this is the embolus; the other is intimately associated with the embolus and is known as the conductor of the embolus, or the conductor of the style, or, simply, as the conductor. A comparatively simple example of this group of palpi is that of Atypus bicolor. Here the terminal part of the conductor is a broad concave plate (Fig. 100), in which the terminal portion of the embolus rests. A more complicated form of the apical division of the bulb exists in Hypochilus thorellii (Fig. 95). Here the embolus is coiled about the conductor, the terminal part of which is concave so as to support the terminal portion of the embolus; the tip of the conductor bears a delicate membranous flap. In Hypochilus the tarsus bears a branch which supports a prominent bunch of bristles (Fig. 95, p. c); this may be a rudimentary form of paracymbium, a part that is well-developed in Pachy- gnatha. A somewhat similar condition exists in Pachygnatha (Fig. 101). Here the proximal part of the embolus is coiled about the conductor, which is a broad twisted plate; and the terminal portion of the embolus is supported by the corre- sponding part of the conductor. When at rest the apical division of the bulb Fig. 99. PALPUS OF DYSDERA INTERRITA ..■cym. cmb.- con. mm mm '~ t. m Fig. 100. TARSUS OF ATYPUS BICOLOR I IO The External Anatomy of Spiders rests in the concave tip of the cymbium; bui in the specimen figured the bulb has been extended so as to show the parts better; and the embolus and conductor have been separated at the tip. In Pachygnatba the tarsus is divided into two distinct parts, which are joined by a movable articulation at the base. The larger part is the cymbium (Fig. 101, cym.) the smaller part, the paracymbium: this is termed by some writers the accessory branch of the tarsus (Fig. 101, p. c). The cymbium and the paracymbium re- semble the other segments of the palpus in the nature of their cuticula and in the fact that they are clothed with hairs. THE MORE SPECIALIZED TYPES OF PALPI In the development of the bulb of the male palpus in the more specialized families of spiders there has been evolved an exceedingly complicated organ, which is difficult to understand, on account of its small size and the fact that when — emb. m.d. -p. c. Fig. ioi. GENITAL is I LB OF PACHYGNATHA EXTENDED a. d. m.d. b.d. Fig. 102. EXPANDED BULB OF LIXYPHIA PHRYUIANA at rest it is compactly folded. Fortunately when such a palpus is boiled in a solu- tion of caustic potash (10%) the bulb expands so that its parts can be seen: and it preserved in glycerine, it remains flexible, so that it can be easily manipulated. I he expanded bulbs figured below were prepared in this way. Even with the best of preparations, it is sometimes difficult to make out the relation of parts; this can be most easily accomplished by the use of a stereoscopic binocula; microscope. I he extreme specialization of the palpi of males is marked chiefly by the development of hjsmatodocha, to be described later, and by an increase in the number of distinct parts and appendages oi tin- bulb. I he maximum degree ol specialization is to be found in the \r.inein.e, of which the palpi ol several species of t>,in,:i are described later. I he understanding of the relation of the parts of ilw hu'lh in tbi* genus will be facilitated by a study first ol a more simple form, such .as is found in the Linyphiids. 1 I I The External Anatomy of Spiders The Linyphia Type of Palpus. — The very common Linyphia phrygiana will serve as an example of the Linyphiidae. As in Pacbygnatha, just described, the body of the tarsus of Linyphia consists of two parts; the cymbium (Fig. 102, cym.), and the paracymbium (Fig. 102, p. c). The alveolus is a circular- cavity near the base of the cymbium. When the bulb is expanded, the three divisions of it are distinctly separated; there being a slender neck between the basal division (Fig. 102, b. d.) and the middle division (Fig. 102, m. d.) and also a similar slender neck between the middle di- vision and the apical division (Fig. 102, a. d). The wall of the basal division of the bulb consists of two parts; the basal hasmatodocha, and the subtegulum. The basal hamatodocha. — The genital bulb is attached to the cymbium, within the alveolus, by means of a sac-like structure, which, ordinarily, is incon- spicuous or completely concealed by other parts of the bulb, but which is very conspicuous in the expanded bulb (Fig. 102, b. /;.). This has been named the hamatodocha from the fact that at the time of pairing it is distended with blood. The wall of the haematodocha appears to consist of elastic connective tissue; hence the name spiral muscle applied to it by Menge is inappropriate. In fact no muscle tissue has been found within the genital bulb. As similar extensible blood sacs are present in more distal parts of the bulb of many spiders, 1 suggest that this one be termed the basal hccmatodocha. The subtegulum. — The proximal end of the basal haematodocha is attached to the cymbium, the distal end, to a ring-like sclerite, for which 1 propose the term subtegulum (Fig. 102, s. teg.) . The middle division of the bulb. — The middle division of the bulb (Fig. 102, m. d.) is that part which contains the chief portion of the receptaculum sem- inis, the reservoir; its wall is the tegulum, and it bears an appendage, the median apophysis. The tegulum. — The term tegulum was applied by Wagner to all of the more densely chitinized parts of the wall of the genital bulb; but as it is desirable that the different sclerites should bear distinctive names, I propose that this term be restricted to the sclerite that forms the wall of the middle division of the bulb. In Linyphia, the tegulum, in this restricted sense is a ring-like sclerite (Fig. 102, teg.). The median apophysis. — Arising within the distal margin of tegulum there is an appendage, only the tip of which is shown in the view of the bulb figured here (Fig. 102, m. a.); this is the median apophysis. In many spiders this appendage is very conspicuous; and to it have been applied several names. In fact in several instances a writer has applied different names to this part in his descriptions of different genera. Among the names that have been applied to it are clavis, unca, and scopus. The term median apophysis occurs frequently in descriptions, and is the older name for this part. The median apophysis is articulated to the middle division of the bulb near the point from which the apical division arises; and in some cases, as in Aranea, it appears to be more closely articulated with a basal segment of the apical di- vision, the radix, than it is with the tegulum. The apical division of the bulb. — This division includes that portion of the bulb which lies distad of the middle division; it consists of two subdivisions: the conductor and the embolic subdivision. The embolic subdivision is traversed by the ejaculatory duct and is composed of several distinct parts. In fact the multiplication of parts of the embolic subdivision is the most characteristic feature of the more specialized types of palpi as contrasted with the intermediate type described above. The conductor. — The conductor (Fig. 102, con.) is easily recognized by its relation to the embolus, which rests upon it, and by its membranous texture. Its attachment to the middle division of the bulb is by means of an exceedingly delicate membrane. In Linyplna the embolus rests upon the conductor throughout its length; but in many genera the palpi of some of which are described later, the function of the conductor is evidently to protect the tip of the embolus in the unexpanded I 12 The External Anatomy of Spidus bulb. In many cases the embolus is very long while the conductor is short; but in every case the embolus in the unexpanded bulb occupies such a position that its tip is protected by the conductor. In most cases the conductor can be recognized at a glance by its peculiar texture; sometimes it is chitinized to a considerable extent, but even then it usually has a membranous margin; and in any . a*e it can be recognized by its relation to the tip of the embolus in the unexpanded bulb. The embolic subdivision. — Closely connected with the membranous base of the conductor is the base of a separate subdivision of the apical division of the bulb; as this portion bears the embolus it may be termed the embolic sub- division. The radix and the stipes. — Immediately following the membranous neck that connects the middle and the apical divisions of the bulb and parallel with the membranous base of the conductor, there are two segments of the embolic sub- division; to the basal one of these ! apply the term radix (Fig. 102, ra); and to the second, the term stipes (Fig. 102, 5/.). For con ,&** a more distinctly segmented condition of the base of the embolic subdivision see the figures emb. '-■ cynt. Fig. 103. PALPUS OF LINYPHIA PIIRYGIANA Fig. 104. PALPUS OF ARANEA FRONDOSA of Eriophora circulata given later (Fig. 109 and 1 10), where the corresponding parts bear the same letters. The embolus. — The organ through which the ejaculatory duct opens, the embolus, is comparatively simple in Linyphia, being a short spine-like part (Fig. 102, emb). The lateral subterminal apophysis. — In Linyphia phrygiana there is developed a remarkable plate-like apophysis, which serves to protect the exposed face of the unexpanded bulb. In Fig. 102 (/. st. a.), only the edge of this apophysis is shown; but in Fig. 105. the broader face of it is represented. I designate this {he lateral suhterminal apophysis as it occurs on the Literal aspect of the unexpanded bulb, and also to distinguish it from an apophysis developed on the opposite face of the bulb in a suhterminal position, which occurs in certain other genera, The terminal apophysis. — The embolic subdivision ends in a strongly chitinized lobe, which may be designated the terminal apophysis 1 1 ig, 102. / a.). To apoph- yses of this kind Menge applied the term retinacula; but as this term predicates their function, which in some cases is obviously not that implied by the name, I prefer apophysis with a modifying term indicating the position of the particular apophysis described. 113 The External Anatomy of Spiders The Aranea Type of Palpus. — I have selected the palpus of Aranea frondosa as an example of an extremely specialized palpus. In Fig. 104 the entire palpus, with the bulb unexpanded, is represented slightly twisted so as to show the ventral aspect of the proximal segments and the lateral aspect of the bulb. The proximal segments of the palpus. — This account of the palpi of male spiders is devoted almost entirely to a discussion of the parts of the tarsus, the proximal segments being well understood; there are, however, a few features of these segments in the aranea type that merit attention here. Upon the coxa there is a prominent spur, the coxal spur (Fig. 104, c. s.)\ and upon the inner side of the femur near its base, there is a groove, the femoral groove, into which the coxal spur fits when the palpus is extended forward. The presence or absence of this spur and groove is an important generic characteristic in the Araneinaj. The patella bears two prominent spines at its apex (Fig. 104, p.). This is also true in the males of several other Fig. ios. LATERAL ASPECT OF AN EXPANDED BULB OF ARANEA FRONDOSA Fig. 106. MESAL ASPECT OF AN EXPANDED BULB OF ARA- NEA FRONDOSA genera; but in the greater number of genera of the Araneinae there is only a single spine in this position. The most striking feature of the tibia is its shortness, it being of about the same length as the patella. The tarsus.- — As in Linyphia. the tarsus of Aranea consists of two parts: the cymbium and the paracymbium. Hut in Aranea the paracymbium (Fig. 105, p. c.) is merely a prominent apophysis arising from the base of the cymbium and is not articulated with the cymbium by a movable joint as in Linyphia and in Pachygnatha. The alveolus is much more extended than it is in Linyphia; here it occupies nearly the whole length of the cymbium (Fig. 105, a). The unexpanded bulb. — In the unexpanded bulb of Aranea frondosa, the subtegulum (Fig. 104, s. teg.), tegulum (Fig. 104, teg.), and a terminal lobe of the apical division of the bulb, bearing a long and slender terminal apophysis (Fig. 114 The External Anatomy of Spiders 104, t. a) are visible. Two prominent appendages can also be seen; the median apophysis (Fig. 104, m. a.) and the conductor (Fig. 104, con.) The expanded bulb. — Two figures of the expanded bulb are given here; Fig. 10s represents the lateral aspect of the bulb, the aspect that is exposed when the bulb is not expanded; and Fig. 106, the mesal aspect, the one that is next the cymbium in the unexpanded bulb. The basal haematodocha is essentially the same as in Linyphia (Figs. 105 and 106, b. /'.). The subtegulum is a ring-like sclerite but its form is like that of a seal-ring being narrow on the mesal aspect of the bulb and wide on the lateral aspect (Fig. 106, s. teg.). This wider part of the subtegulum is all of it that is commonly ob- served and has been termed the lunate plate. the specimen represented in Fig. 106 was more fully expanded than that used for Fig. 105. In the more expanded specimen there is evident a large haematodocha between the subtegulum and the tegulum; this 1 designate the middle haematodocha (Fig. 106, m. h.) The dark axial object seen through the wall of the middle haematodocha is the fundus of the receptaculum seminis (Fig. 106, fit.). The tegulum is also a ring-like sclerite, which is broad on the lateral aspect of the bulb (Fig. 105, teg.), and is narrow on the mesal aspect (Fig. 106, leg.). The median apophysis (Fig. 104 and 105, m. a.) is a conspicuous appendage, which projects from the ventral side of the bulb. Although the position of this appendage in Linyphia, in which the middle and apical divisions of the bulb are distinctly separated, shows that the median apophysis is an appendage of the middle division, in Aranea it appears to be articulated with the base of a proximal segment of the apical division, the radix. the conductor (Fig. 106, con.) arises at the base of the apical division and is closely connected with the tegulum. The radix (Fig. 106, ra.) is much larger than in Linyphia. Here it forms the wall of one side of the basal segment of the embolic division of the apical division. I hat this is the case is more clearly shown in the bulb of Eriopbora circulata (Figs. 1 10 and 111, ra.), where the segmentation of the embolic subdivision is much more marked. The stipes (Fig. 106, st.) is also much larger than in Linyphia; it is articulated with the distal end of the radix. Like the radix, the stipes forms the wall of one side of a segment of the embolic subdivision of the bulb, a fact which is also well shown in the bulb of Eriophora circulata (Figs. 1 10 and 1 1 1, st.). The embolus is borne by the embolic subdivision distad of the stipes; it pro- jects ventrad between the distal end of the stipes, which is mesadof it, and the conductor, which is laterad of it in the unexpanded bulb. In the specimen repre- sented in Fig. 106, the distal end of the stipes and the embolus have been pushed away from the conductor in the expanding of the bulb. The distal beematodocba. — The most striking feature of the embolic subdivision in the aranea type is the presence of a large haematodocha, which when expanded overshadows all other parts. This haematodocha I designate the distal bamato- docba (Figs. 105 and 106, d. /;.). It is doubtless due to the development of this haematodocha that the radix and the stipes are restricted to one face of their re- spective segments of the apical division in Aranea frondosa, the remaining parts of the wall of these segments forming a part of the distal haematodocha. The mesal subterminal apophysis. — On the mesal aspect of the bulb, there arises from the distal haematodocha a prominent apophysis (Fig. 106, m. si. a.); this may be termed the mesal subterminal apophysis. 'The lateral subterminal apophysis. — On the lateral aspect there is also an apophysis borne by the distal haematodocha (Fig. 103, /. st. a.); this may be termed the lateral subterminal apophysis. 1 he terminal apophysis. — In Aranea frondosa, the tip of the embolic sub- division of the bulb ends in a spear-shaped apophysis (Fig. 105, /. a.); this may be termed the terminal apopby Tin Palpus 01 Arani \ Ocellata.' — A glance al the palpus of Aranea ocellata will show that it is of essentially the same type as that of Aranea frondosa I I --> m.a. b. h. .p.c. Fig. 107. LATERAL ASPECT OF AN EXPANDED BULB OF ARANEA OCELLATA Fig. 108. UNEXPANDED BULB OF ERIOPHORA CIRCULATA emb. m.a. -emb. d.h. Fig. log. UNEXPANDED BULB OF ERIOPHORA CIRCULATA i p.c. Fig. no. EXPANDED BULB OF ERIOPHORA CIRCULATA I l6 The External Anatomy of Spiders but is different in some details. It is figured here to illustrate the kind of varia- tions in form that serve to distinguish closely allied species (Fig. 107). The median apophysis differs markedly in form from that of A. frondosa; the tegulum bears a small but distinct apophysis; the lateral subterminal apophysis bears two prominent teeth; and the terminal apophysis is lacking, the embolic subdivision ending in a blunt lobe. The Palpus of Eriophora Circulata. — The most striking modification of the aranea type of palpus, taking the palpus of Aranea frondosa as typical, is that of Eriophora circulata, which is the most complex palpus that i have studied. In the unexpanded bulb, there appears to be no resemblance to the bulb of Aranea frondosa. In Eriophora circulata (Figs. 108 and 109), the bulb is very large and the cymbium comparatively small and narrow (Fig. 109, cym.). The basal hzema- todocha (Fig. 108, b. h.) is conspicuous, which is a result of the other parts of the bulb being twisted into unusual positions. The median apophysis is large and projects beyond the tip of the bulb (Fig. 108, m. a.). But the most remarkable feature is an elbowed structure on the mesal aspect at the base of the bulb (Fig. 109). The fact that the ejaculatory duct can be traced throughout the length of this elbowed structure gave the first definite clue to the relations of the -emb. parts of the bulb. The part contain- ing the ejaculatory duct evidently Wt.a. jnl »i. st. a. 1 m.a.-- Fig. in. EXPANDED BULB OF ERIOPHORA CIRCULATA Fig. 112. UNEXPANDED BULB OF \KA.\EA GIGAS pertains to the apical division of the bulb, although it appears to arise from the base of the bulb. When the bulb of Eriophora circulata is expanded and untwisted, as occurs in the process of expansion, the relations of the parts are more easily seen. Figures 1 10 and 1 1 1 represent two views of a preparation of this kind. If Fig. 1 1 1 be studied it will be seen that the relations of parts are essentially the same as in Aranea frondosa (Fig. 106); the basal ha;matodocha, subtegulum, and tegulum follow in the same sequence; the median apophysis and the conductor project from beneath the tegulum in the corresponding positions, and the elbowed structure, which in the unexpanded bulb appears to arise at the base of the bulb is here clearly seen to be the embolic subdivision of the bulb. I he most remarkable differences are the lack of a prominent distal ha*matodocha and the fact that the radix (Fig. 111, ra.) and stipes il ig, in, st.) are each .1 complete cylinder, instead of merely forming one face of the wall of .1 segment of the apical division, as in Aranea frondosa. At the distal end of the stipes, between this part and the embolus and the terminal apophysis, thfere is a vestigial distal h.ematodocha (Fig. 110, d. h.). I I The External Anatomy of Spiders I n this species there is an apophysis, which like the median apophysis, is joined by a flexible articulation to the tegulum within the cup-like cavity formed by the distal margin of the tegulum (Figs. 109 and 1 1 1, p. m. a.); this may be termed the paramedian apophysis. As 1 have not found this apophysis in other palpi, I do not consider it a fundamental part. The Palpus of Aranea Gigas. — The preceding species, Eriophora circulata, and several others have been separated from Aranea by Pickard-Cambridge and placed in the resurrected genus Eriophora of Simon. The peculiar form of the gen- ital bulb in Aranea circulata appears to sustain this separation. Rut in the palpus of Aranea gigas (Figs. 1 12 and 1 13) we find a form intermediate between the aranea type and what may be termed the eriophora type. In the unexpanded bulb of Aranea gigas (Fig. 112) the parts are twisted so as to render the basal haematodocha conspicuous as in Eriophora circulata; but otherwise there is little similarity in appearance to either this species or to Aranea frondosa. />. c. - con. pet.- ^IS^|-"'' Fig. 113. EXPANDED BULB OF ARANEA GIGAS Fig. 114. EXPANDED BULB OF DOLOMEDES FONTANUS In the expanded bulb (Fig. 113) it can be seen that the embolic subdivision, is intermediate in form between the two types, resembling the aranea type in having a large distal haematodocha and a well-developed median subterminal apophysis; and resembling the eriophora type in the form of the embolus, which is lamelliform (Fig. 1 13, 2). The Pisaurid Type of Palpus. — In the family Pisauridae there is a type of palpus which, while it resembles the aranea type in its more general features, differs from that type. in several important particulars. The palpus of Dolomcdes jontanus (Figs. 1 14 and 1 1 5) may be taken as an example of this type. A study of an expanded bulb of this species (Fig. 114) reveals the following characteristics: There is a well developed petiole of the bulb (Fig. 1 14, pet.), which in this species consists of two nodes with an unchitinized internode. The sub- tegulum bears very prominent anelli (Fig. 1 14, an), which are described in a later paragraph. The median apophysis is prominent (Fig. 1 14, m. a.). The conductor (Fig. 1 14, con.) is extremely membranous. The radix and the stipes are not developed as distinct segments. The etkbolus is of the spiral type (Fig. 1 14, emb.) Il8 The External Anatomy of Spicier. ex -a.. The terminal apophysis is modified into an organ for the support of the emh< I I rig. i 14. ful.), which may be termed the fulcrum of the embolus. I his type of terminal apophysis has been termed, incorrectly, the conductor. The true coi ductor in this species, as in all others studied, is an organ whose function is to protect the tip of the embolus in the unexpanded bulb. At the base of the terminal apophysis, at the point where the embolus arises, there is a lamelliform lateral subterminal apophysis (Fig. 1 14, st. a.). In the unexpanded bulb (Fig. 1 1 5), the long embolus makes a cun e in 1 In- distal end of the alveolus beyond the end of the bulb. The fulcrum is applied against the embolus on its concave side, and has a furrow on its distal face within which the embolus rests. The distal part of the conductor is wrapped about the tip of the combined embolus and fulcrum, serving, as in all other cases observed, as a protection to the tip of the embolus. The Thomisid Type of Palpus. — In the family I homisidae, there occurs a striking modification of the palpus, which consists of the absence of the conductor of the embolus and, in certain members of the family, of a special- ization of one edge of the cymbium for the protection of the tip of the embolus in the unexpanded bulb. To this specialized part cf the cymbium 1 have applied the term tutaculum (tu-tac'u-lum); it is described and figured in the general account of the Thomisidae on a later page. It is best developed in the genus Xysticus. The Anelli of the Subtegulum. — In Aranea, the chitinized part of the wall of the basal division of the bulb, the subtegulum, is reduced to a ring-like sclerite (Fig. 1 16, 1.); but in certain other genera, the subtegulum is cup- shaped or basket-like. In Agelena navia (Fig. 1 16, 2.), one side of the subtegulum is greatly thickened; at the prox- imal end of this thicken- ing, which corresponds to the lunate plate, t here is a condyle, which articulates with the pet- iole; and at the distal end, there is a condyle, which articulates with the tegulum. The other side of the cup-like subtegulum contains in its wall several parallel, incompletely ring-like sclerites; these may be termed the anelli of the subtegulum. In Dolomedes fontanus (Fig. ii<>. the anelli of the subtegulum are greatly thickened and form prominent, projecting ridges. It is probable that the presence or absence of the anelli of the subtegulum, and their nature when present will atford characters of use for taxonomic purposes The Different Types 01 Embolus.— 1 he form of the embolus \ aries greatly in dilferent species of spiders. Two principal types can he recognized, the connate and the free; and the free type includes three subtypes. The connate type of embolus. — In the connate type, the embolus is not separate from the middle division of the bulb, hut is merely a more slender continuation of it, as in the tarantulas. Loxosceles (Fig 96), and l-nulna. The tree type of embolus. — In the free type "t embolus, there an- one or p movable articulations between the embolus and the middle division of the bulb Fig. 115. UNEXPANDED BULB OF DOLO.MKDKS FONTAN1 - Fig. 116. THREE KINDS OF SUBTEGULl M I K) Fig. 117. THREE TYPES OF EMBOLUS The External Anatomy of Spiders In the free type, the embolus varies greatly in form; but the different forms can be grouped under three heads; coniform, iamelliform, and spiral. A coniform embolus. — In this type, there may be a broadly expanded base; but the projecting part of the embolus is a straight or slightly curved cone. The embolus of Aranca jrondosa (Fig. 117, 1.) is an example of this type. A Iamelliform embolus. — In this type the embolus is flattened, and may bear a greater or less number of apophyses; an example of this type is found in Leptby- pbantes minuta (Fig. 117, 2.). A spiral embolus. — - In the spiral type, as seen in Agelend, for example, the em- bolus is long, slender and coiled; and, in a well-expanded specimen, it is seen to be composed of three distinct parts; first, the wall of the convex side is densely chitinized, forming a gutter-like sclerite, which may be termed the trunk of the embolus (truncus) (Fig. 117, 3, t. f.); second, the greater part of the wall of the embolus is membranous, and forms a loose flap along the concave side of the or- gan, which contains the ejaculatory duct; this flap (Fig. 117, 3, p. p.) may be designated the pars pendula of the em- bolus; third, at the dis- tal end of the pars pendula, there is a triangular, chitinized area, through whicli the ejaculatory duct opens (Fig. 117, 3, a. s.), this may be termed the apical sclerite of the embolus. The pars pendula and the apical sclerite may be completely withdrawn into the trunk of the embolus, so that only the latter is visible; the embolus then appears to be merely a strongly chitinized style; it is in this condition that it is usually seen and described. CONCLUSION In the preparation of this account many palpi other than those figured here have been studied; and it is believed that the series examined has been sufficiently large to warrant the conclusions given regarding the fundamental parts of the genital bulb. There remains to be determined the manner in which the different types of palpi have been specialized in other families of the order, and the details of the modifications characteristic of genera. This, however, is too great an under- taking to be attempted at this time; and must be left for those who monograph the different families. I wish, however, to urge the importance of describing palpi from expanded specimens. A large proportion of the figures of palpi that have been published being of unexpanded examples, show comparatively little of the structure of this organ. The labour involved in expanding the bulb of a palpus is very little; a preparation can be made in five minutes; and in no other way can so much be done to make possible a description that will describe. The following tabular statement shows the relations of the fundamental parts of the tarsus in the more specialized types of palpi; not all of these parts are invariably present, and frequently subordinate apophyses are developed. Body of the Tarsus C/mbium, containing the alveolus Tutaculum (in the Thomisida?) Paracymbium 120 The External Anatomy of Spiders Genital Bulb Internal parti Receptaculum seminis Fundus Reservoir Ejaculatory duct External parts Basal di\ ision of the bulb Basal haematodocha Petiole Subtegulum Lunate plate Anelli of the subtegulum Middle division (if the bulb Middle haematodocha Tegulum Median apophysis Paramedian apophysis Apical division of the bulb Conductor Embolic subdivision Radix Stipes Embolus Body of embolus Pars pendula Apical sclerite of the embolus Distal ha'matodocha Lateral subterminal apophysis Mesal subterminal apophysis Terminal apophysis, sometimes developed into a fulcrum NAMES OF THE PARTS OF THE PALPUS AND ABBREVIATIONS USED FOR THEM IN THE ILLUSTRATIONS Accessory branch = paracymbium. Mesal subterminal apophysis, m. st. a. Alveolus, a. Middle division of the bulb, m. d. Anelli of the subtegulum, an. Middle haematodocha, m. h. Apical division of the bulb, a. d. Paracymbium, p. c. Apical sclerite of the embolus, a. s Paramedian apophysis, p. m. a. Basal division of the bulb, b. d. Pars pendula of the embolus, p. p. Basal haematodocha, b. b. Patella, p. Clavis = median apophysis Petiole of the bulb, pet. Conductor of the embolus, con. Radix, ra. Coxa, c. Receptaculum seminis, r. s. Coxal spur, c. s. Reservoir, res. Cymbium, cym. Scopus = median apophysis. Distal haematodocha, d. h. Spiral muscle = haematodocha. I jaculatory duct, ej. d. Stipes, st. Hmbolic subdivision of the bulb, e. s. Style = embolus. Embolus, enib. Subtegulum, s. teg. Femur,/. Tegulum, teg. Fulcrum, Jul. Terminal apophysis, t. a. fundus of the receptaculum seminis, fu. Tibia, t. Lateral subterminal apophysis, /. st. a. Trochanter, tr. Lunate plate = subtegulum in part. Trunk of the embolus, i. e. Median apophysis, m. a. Tutaculum, tu. THE THORAX i The thorax is that part of the cephalothorax which bears the four pairs of legs. It is either slightly separated from the head by a furrow, or completely coalesced with it. The Tergum of the Thorax.— The dorsal aspect of the thorax, or the tergum, is by far the most prominent part of this 12 I The External Anatomy of Spiders region of the body. It extends forward on each side of the wedge-shaped hind end of the head, and covers to a greater or less extent the sides of the thorax. It is often marked by a median furrow and several radial furrows (Fig. 118); these are lines along which muscles are attached to the inner surface of the body-wall. The median furrow is sometimes called the dorsal groove. The Sternum. — The plate forming the ventral wall of the thorax is the sternum (Fig. 119, 5.); it occupies the entire space between the two rows of legs; and usually each lateral margin bears four notches for the reception of the coxae of the legs. The sigilla (sig'il-la). — In many tarantulas the sternum is marked by circular or oval, impressed, bare spots, normally four on each side; these are termed the sigilla. It should be noted that sigilla is a plural noun; the term sigillae, sometimes used, is, therefore, incorrect. The Epimera (ep-i-me'ra). — Correlated with the great development of the tergum of the thorax there is a marked re- duction of the lateral portions, each of which usually consists of a narrow band between the legs and the tergum. In some cases this band consists of a series of four sclerites, one above each leg. These sclerites are termed the epimera; each epimeron represents the pleural portion of a segment. The Legs. — There are always four pairs of legs. Each leg consists of seven segments which are named, beginning with the one next the body as follows: coxa, trochanter, femur, patella, tibia, metatarsus and tarsus (Fig. 120). The tarsus usually bears at its tip two or three claws. In certain spiders, which have very long and slender legs, the tarsus is rendered flexible by a large number of secondary joints or "false articulations." The prxtarsus (prae-tar'sus). — The claws are outgrowths of a small terminal portion of the leg which is not ordinarily distinguished from the tarsus. This terminal part with its appendages has received the name prcetarsus (de Meijere 'oi). As a rule the praetarsus in spiders is withdrawn into the pro- jecting ventral part of the tarsus; but sometimes it is a distinct segment (Fig. 121). This segment is termed by Simon ('92, p. 52) the onychium, an unfortunate use of the term, as ordinarily it is used as a synonym of empodium. (See p. 123.) 122 /TV 1 iV '-*^ K§ B* w> V Fig. 118. CARAPACE OF A TARANTULA Fig. rig. VENTRAL ASPFXT OF CEPHALOTHORAX OF DLOBORUS s, sternum Fig. 120. LEG OF A SPIDER i, coxa 2, trochanter .5, femur 4, patella 5, tibia 6, metatarsus 7, tarsus Fig. 121. TIP OF THE LEG 01 \ SPED! R SHOWLWG Till. PR I fARSI B Fig. 122. (I WS Wl' VCI ESSORV CLAW - "l \ SPIDER 123 The External Anatomy of Spiders Fig. 123. A TENENT HAIR FROM THE EMPODIUM OF CLUBIONA The daws. — Each tarsus of the legs is armed with two or three claws. When three claws are present, they can be desig- nated as the paired daws and the third daw respectively. The paired daws are placed side by side at the tip of the upper surface of the tarsus, or of the praetarsus if it is distinct; they are usually armed with a series of teeth (Fig. 121). The third claw is a modified empodium (see below); when present, it is situated below the paired claws. It is smaller than the paired claws, and is sometimes armed with a small number of fine teeth. Usually the terminal portion is bent down rather abruptly (Fig. 121). The empodium (em- po'di-um). — When the terminal portion on the middle line of the praetarsus projects between or below the paired claws it is termed an empodium. Sometimes the em- podium is claw-like; it then constitutes the third claw described above; sometimes it is a cushion-like pad or adhesive lobe; and sometimes it is not devel- oped as a distinct part. Many terms have been applied to this part; among them a.rearolium,onychium, palmula, plantula and pul- villus. The accessory daws. — In many spiders, especially those that spin webs, the tip of the tarsus is armed with several claw-like opines; these have been termed the accessory daws (Fig. 122). The accessory claws are very different morphologically from the true claws, being modified hairs each produced by a trichogen; while the true claws are spine-like projections of the body-wall formed by many hypo- dermal cells. Fig. 124. TIP OF TARSUS OF CLUBIONA WITH TERMINAL TENENT HAIRS 124 The External Anatomy of Spiders The terminal tenent hairs. — The tarsi of spiders are armed, in many species, with hairs of the type known as tenent hairs, i. e., hairs that are dilated at the extremity (Fig. 123), and which serve to aid the animal in clinging to smooth surfaces, probably as in insects by means of an adhesive fluid excreted through the cavity of the hair. A bundle of such hairs which exists in certain spiders at the tip of the tarsus just below the claws may be designated as the terminal tenent hairs (Fig. 124). This bundle is often divided into two by a smooth line; these bundles are the fasciculi unguiculares or claw-tufts of certain writers. A small sclerite upon which the bundle or bundles of terminal tenent hairs are borne is sometimes referred to as the hypopodium; this is sometimes covered by the empodium. The scapula (scop'u-lae). — The lower surface of the tarsus and the metatarsus are often armed with tenent hairs. A brush of such hairs is termed a scapula (pi. scopulcc). The scopula Fig. CALAMISTRUM OF ULOHORUS GEXKT'LATUS and the terminal tenent hairs are frequently both present. A thick clothing of ordinary hairs in this position is not a scopula. The calamistrum (cal-a-mis'trum). — Those spiders that pos- sess the peculiar spinning organ known as the cribellum have also on the upper margin of the metatarsus of the hind legs one or two rows of curved spines (Fig. 123); these constitute the calamistrum. The calamistrum plays the part of a hackle in the formation of the hackled band, characteristic of the webs of these spiders. Male spiders on reaching the adult stage either lose the cribel- lum and calamistrum or retain them in a vestigial condition; but such males can be recognized by the wide separation of the fore spinnerets. The lyriform argans. — Near the distal extremity of each segment of the leg except the tarsus there are one or more minute 123 r. V 1 he External Anatomy of Spiders organs, which have been termed the lyriform organs (Fig. 126). These are believed to be sense organs, and are discussed under that head in the next chapter. Leg formula:. — The relative lengths of the different pairs of legs often afford distinctive char- acteristics, which are much used in descriptive works. The four pairs of legs are numbered from before back- ward; and in descriptions their relative lengths are indicated by a formula consisting of the numerals 1, 2, 3, and 4 arranged in the order of the relative lengths of the legs of the spider de- scribed beginning with the numeral indicating the longest pair of legs. Thus the formula 1432 indicates that the first pair of legs is the longest and the second pair the shortest. Where two or more pairs of legs are of equal length the fact is indicated bv placing a bar or bracket above the Fig. 126. LYRIFORM ORGANS " , . , , , of argyrodes numerals, thus the formula 2341 indicates that the third and fourth pairs of legs are of the same length. Spine formula:. — The number and arrangement of the spines on the segments of the legs are often indicated by formulae. Thus if there are two rows of spines of three each under the tibia of the first legs and two rows of two each under the metatarsus of these legs, the fact is indicated as follows: spines, tib.I., 3-3, met. I, 2-2. THE ABDOMEN The abdomen of spiders is more or less sac-like and almost always without traces of segmentation except in a very small area at its caudal end. In most spiders the abdomen is of an elongated, rounded form; but an exceedingly great variation in the form of this region exists. The Parts of the Abdomen. — Owing to the almost total lack of segmentation comparatively few distinct parts can be recognized in the abdomen; spiders differ greatly in this re- spect from insects, in which the abdomen is composed of a 126 The External Anatomy of Spiders series of well-marked segments. The following parts can be recognized in the abdomen of spiders. The pedicel. — In all spiders the abdomen is joined to the thorax by a slender stalk, the pedicel, which is usually concealed from above by the convexity of the part immediately following it. In certain spiders, which are ant-like in form, the pedicel of the abdomen is conspicuous; but in many of these a prolonga- tion of the thorax enters into the composition of the pedicel. In the dorsal wall of the pedicel there is a slender, longitudinal sclerite, which is termed the brum of the pedicel; in some genera the lorum is divided by a transverse Fig. 127. LORUM OF THE PEDICEL OF P1SAURIXA Fig. 128. ARANEA FROXDOSA, SHOWING FOLIUM suture (Fig. 127). In some forms there is also a sclerite in the ventral wall, the plagula (plag'u-la). The plagula is well- developed in the Dysderidae. The muscle-impressions. — On the dorsal aspect of the abdo- men, there are several pairs of muscle-impressions; these are small, hardened, depressed points, which, like the radial furrows of the thorax, indicate the points of attachment of muscles to the body-wall. There is also near the base of the abdomen a median, unpaired muscle-impression, which is more or less prominent. In some spiders there are muscle impressions on the ventral aspect of the abdomen. 127 The External Anatomy of Spiders The folium. — The dorsal aspect of the abdomen in many spiders is marked by an area with scalloped margins (Fig. 128); this area on account of its leaf-like outline is termed the folium (fo'li-um). The folium is frequently marked with spots; and its margin is often a double stripe, the inner part of which is dark and the outer part light. The postabdomen. — At the caudal end of the abdomen there is a small, conical or semicircular portion, which, when seen from above, appears to consist of two or three segments; this is the greatly reduced postabdomen. In the embryo, the postabdomen is much more distinct, resembling in a striking degree the postabdomen of scorpions (see Korschelt and Heider '99, Vol. 111., p. 50). The epigastrium. — On the ventral aspect of the abdomen, the basal portion is usually more convex than the remainder of this aspect of the abdomen and is sometimes more densely chiti- nized; this area is termed the epigastrium (Fig. 129, e.). The epigastric furrow. — A furrow separating the epigastrium from the more caudal portion of the abdomen is known as the epigastric furrow (Fig. 129, ef.). In this furrow there is, on the middle line of the body, the opening of the reproductive organs, and at each end, the opening of a lung. The furrow of the posterior spiracle. — This is a transverse furrow on the ventral aspect of the abdomen, a short distance in front of the spinnerets, in which is situated the posterior spiracle, in most of those spiders that have only three spiracles. In a few cases, as in Anyphazna and Glenognatha, the third spiracle is situated near the middle of the ventral aspect of the abdomen. The abdominal sclerites.- — Owing to the lack of segmentation in this region of the body comparatively few sclerites can be recog- nized on the abdomen, still in some spiders the abdomen bears one or more distinct sclerites. There may be a dorsal sclerite, one on the dorsal aspect of the abdomen; an epigastric sclerite, one on the epigastrium; a ventral sclerite, one in the region behind the epigastric furrow; and an infra-mammilliary sclerite, a semi- circular one situated in front of the spinnerets, i. e., below the spinnerets when the spider is hanging suspended by a thread. The spiracles. — The spiracles or openings of the respiratory organs, are of two quite distinct kinds; one leading to lung-like organs, the lung-slits, and one leading to tracheae of the ordinary type, the tracheal spiracles. 128 The External Anatomy of Spiders The lung-slih. — Of these there are either one or two pairs. The first pair, which is always present except in one small, exotic family (Caponiidae) is situated one at each end of the epigastric furrow. In the tarantulas and in the family Hypochilidae there is a second pair of lung-slits behind the first (Fig. 129). The tracheal spiracles. — In the true spiders except the family Hypochilidae there are ordinary tracheae in addition to the book- lungs. In most cases the ordinary tracheae open by a single spiracle, which is usually situated on the middle line, a short distance in front of the spinnerets; but sometimes this single spiracle is near the middle of the ventral aspect of the ab- domen. In a few spiders there r t /' / iS A Fig. 129. VEXTRAL ASPECT OF ABDOMEN OF A TARANTULA e, epigastrium ef, epigastric furrow Fig. 130. DYSDERA INTERRITA, A TRUE SPIDER WITH A PAIR OF TRACHEAL SPIRACLES BEHIND THE LUNG-SLITS is a pair of tracheal spiracles situated just behind the lung-slits; these can be distinguished from lung-slits by the absence of external indications of book-lungs. Compare Figs. 129 and 130. The epigynum (e-pig'y-num). — The internal reproductive organs open on the middle line of the abdomen in the epigastric furrow. In the male the opening is simple, without any intro- mittant organ, the palpi taking the place of such an organ. In the female the two ovaries open by a common opening, which in some spiders is not accompanied by any specialized chitinous structure; this condition exists in Tetragiuiiha and other genera. But in most of the true spiders (Argiopoidea) there is connected with this outlet a more or less complicated apparatus, which is termed the epigynum. 120 The External Anatomy of Spiders As the epigynum varies greatly in form in different species, even in closely allied ones, it often affords the most distinctive characteristics for recognizing species; but these features are not fully developed until the spider reaches maturity. In its more simple form the epigynum is merely a lid-like plate covering or accompanying the opening of the oviduct; it is a chitinized portion of the cuticula of the segment in front of the epigastric furrow; and it is situated on the middle line of the body at or very near the hind margin of this segment. As explained in the following chapter, there are connected with the internal reproductive organs of the female one or more pouches for receiving and retaining the spermatozoa, the sperma- X Fig. 131. DIFFERENT TYPES OF EPIGYNA a, Pirata montanus b, Trabca aurantiaca c, Lycosa pikei theccE. When there is a single spermatheca, as in Segestria, it opens on the middle line, behind the opening of the oviduct. But in most spiders there are two spermathecae which open separately, one on each side of the opening of the oviduct; and when there is a specialized epigynum, these openings are con- nected with it. In fact it seems probable that the primary function of the epigynum is to receive and direct the palpal organ of the male, and that the various specific forms of epigyna are correlated, in each case, with corresponding specific differ- ences in the palpus of the male; these peculiarities tending to prevent the union of individuals of different species. Frequently, when there is a well-developed epigynum, the openings of the spermathecae are on the outer face of the epigynum and can be easily seen (Fig. 131, a b); as their position varies in different species it is often indicated in specific descriptions. Some writers refer to them as the openings of the epigynum. Even when the openings of the spermathecae are covered by 130 The External Anatomy of Spiders a part of the epigynum, they are sometimes visible in mounted specimens in which the epigynum has been rendered transparent (Fig. 132). Care should be taken not to mistake the glands of the sperma- thecae, which are often dark and show through the body-wall, for the openings of the spermathecae. (See account of these glands in the following chapter.) A secondary function of the epigynum, as an ovipositor, is discussed later. An example of a comparatively simple epigynum is that of Pirata montanus (Fig. 131, a); this is a nearly plain plate, with the two openings of the sperm- athecae near the posterior lateral corners. A somewhat more complicated form is illustrated by the epigynum of Trabea au- rantiaca (Fig. 131, b); in this the plate is depressed or fur- rowed longitudinally, and the depressed area is divided by a ridge-like elevation, which di- vides the depression into two furrows or channels, each of which leads to the opening of the spermatheca of the corre- sponding side; this ridge-like elevation has been termed the guide by Chamberlin ('04), as its function "seems clearly to be that of a guide to the male embolus, controlling the course of the latter and facilitating its entrance to the spermatheca." In many cases the guide extends laterally on each side at its posterior end; this is true to a slight extent in the epigynum of Trabea, but more markedly so in that of many species of Lycosa, where the lateral expansions often conceal the openings of the spermathecae, as in the epigynum of Lycosa ptkei (Fig. 131, c). In some epigyna the posterior portion of the median part of the guide and the anterior edge of the lateral extensions of it are extended horizontally in plate-like expansions, these are termed, by Chamberlin ('08) the lateral plates or ala- of the guide. 131 Fig. 132. EPIGYNUM OF THERIDIOX DIFFERENS 1, surface view 2, view when made trans- parent *, openings of the spermathcae s. spermathecae z, tube leading from the spermatheca to the vagina (alter Emerton) The External Anatomy of Spiders A more complicated form of epigynum is found, for example in spiders of the genus Aranea, where there is developed an ap- pendage which is usually soft and flexible, and which is termed the scape or ovipositor, as it is believed to have a function analogous to that of the ovipositor of insects (Fig. 133). In some cases, however, the form of the scape is such that it is difficult to see how it can function as an ovipositor; and it may be that in these cases it functions during copulation instead of during oviposition. The scape of Aranea gemma (Fig. 134) will serve to illustrate this point. Here the scape is immovable and the spoon-shaped tip seems fitted to receive some part of the palpus of the male rather than to be of use in placing the eggs. When there is a well- developed scape the tip of it is usually more or less spoon-shaped, this part of the scape is termed the cochlear. The basal plate of the epigynum which bears the scape, and which forms a vaulted, porch or hood that covers the opening of the oviduct was named by McCook ('8c)-'93) the atriolum (a-tri'o-lum). A still more complicated form of epigynum is found in some of the Linyphiidae and Argiopidae, where the ovipositor consists of two finger-like projections: first, the more common one, the scape, which arises from the atriolum, and consequently in front of the openings of the oviduct; and second, one which arises behind the opening of the oviduct; this is termed the parmula (par'mu-la). Each of these projections may be grooved on the face next its fellow, the two grooves forming a tube (Fig. 135). The entrance to the reproductive organs of the female is termed the vulva; it is an open space covered by the epigynum. Some writers apply the term vulva to the epigynum. In some spiders there is a well-defined sclerite on each side of the epigynum; these sclerites are termed the lateral scleritcs. The epigastric plates. — There is on each side in front of the lung-slit a hard plate; these are termed the epigastric plates. The Spinning Organs. — The spinning organs are situated near the caudal end of the abdomen, on the ventral aspect, and consist usually of three pairs of spinnerets, to which is added in certain spiders another organ, the cribellum. The spinnerets. — The spinnerets are finger-like in form and usually six in number (Fig. 136), although sometimes there are only four, and the number may be reduced to a single pair. The pairs of spinnerets are usually designated as the upper, 132 Fig. 133. EPIGYNUM OF ARANEA ANGULATA VAR. SILVATICA a, ventral view b, lateral view Fig. 134. EPIGYNUM OF ARANEA GEMMA it Fig. 135. EPIGYNUM OF R-ATHYPHANTES NIGRINUS o, ventral view b, lateral view <; .>' 5 Fig. 136. LATERAL ASPECT OF BODY OF AGELENA SHOWING 1 ill SPINNERETS OF ONE SIDE 133 The External Anatomy of Spiders ||l§gpfSc the lower, and the median, these terms referring to their relative positions when the spider is hanging suspended by a thread; but as very many spiders never assume this position, it is better to designate the three pairs of spinnerets as the fore, middle, and hind respectively. The hind spinnerets usually consist each of two segments, but sometimes of three or even four segments; the middle spin- nerets are not seg- mented; the fore spinnerets consist almost always of two segments each. The sides of the spinnerets are comparatively firm, but the terminal portion is mem- branous; this mem- branous terminal portion constitutes the spinning field. The spinning field is always surrounded by hairs, some of which are simple and some are barbed. These are movable and appear to have some function in the spinning; it is probable that some of them at least are tactile. Sometimes, at least, the spinning field is surrounded by a chit- inous ring, to one side of which is attached the tendon of a flexor muscle (Fig. 137), which probably moves the spinneret as a whole.* The spinnerets represent the fourth and fifth pairs of abdominal legs (the other abdominal legs are lost in the course of the development of the embryo). Each of these legs acquires, at an early embryonic period, a biramose form, like the primitive appendages of the Crustacea, consisting of an axis to which is at- tached an inner endopodite and an outer exopodite. Spinning glands may develop on both rays, and it is thus suggested that the primitive number of spinnerets was eight. No existing spiders are known in which these eight spinnerets are fully developed as functional organs; in Liphistius, however, (which also shows the generalized character of a segmented abdomen) the full number are present, but only the four external ones (exopodites) possess functional spinning glands. In the true spiders, we find present six functional spinnerets, the four large ones being derived from the exopodites of the fourth and fifth pairs of abdominal appendages, while the middle spinnerets are developed from the endopodites of the fifth pair, the endopodites of the fourth pair being altogether wanting or else concerned in the formation of the cribellum or colulus. (Korschelt and Heider, 111., p. 79.) 134 Fig. 137. FORE SPINNERET OF ARANEA a, chitinous ring around the spinning-field b, tendon of flexor muscle c , outlet of cylindrical gland (after Bucholz and Landois) The External Anatomy of Spiders The spinning tubes.— - There are many small tubes distributed over the surface of the spinning field ; these are the spinning tubes; it is through them that the silk is expelled from the body. Usually ach spinning tube consists of two segments, a stouter basal one and a more slender terminal one (Fig. 138). Some spiders have one hundred or more of these spinning tubes on each spinneret. The number of spinning tubes varies greatly in different species, and c d. e. Fig. 138. THE SPINNING TUBES OF ARANEA SEEN IN OPTICAL SECTION a, of aciniform glands b, of pyriform glands c , of ampullate glands </, of cylindrical glands e, of aggre- gate glands (after Apstein) Fig. 140. THE SPIXXERETS AND THE CRIBELLTJM OF AMAUROBIUS Fig. 13Q. HIND SPIXXERET OF STEA- TODA SHOWING TWO SPIGOTS WITHOUT A TIP (after Apstein) Fig. 141. THE CRIBELLUM (il AMAUROBIUS -MORE ENLARGED also in different individuals of the same species. It may be that the number increases with age; but we lack observations on this point. Although the spinning tubes are almost invariably borne by the tip of the spinneret, in a few cases there is one or more on the basal segment of a two-jointed spinneret. There are four different types of spinning tubes: the long and cylindrical (Fig. 138, a); the short and conical (Fig. 138, b); a form much larger than the preceding, which is termed a spigot (Fig. 138, c, d, e); and a spigot without a tip (Fig. 139). Different kinds of silk are spun from the different kinds of spinning tubes. 1 }5 The External Anatomy of Spiders The cribellum (cri-bel'lum). — In certain families there is, in front of the spinnerets, an additional spinning organ, which on account of its sieve-like appearance when slightly magnified, is named the cribellum. The cribellum consists of a transverse plate, which is usually divided by a delicate keel on the middle line of the abdomen into two equal parts (Fig. 140 and Fig. 141). On each of these areas, which are often a little convex, there are very many spinning tubes, the number greatly exceeding the number of spinning tubes borne by the spinnerets. The number of spinning tubes varies greatly, however, in different species; thus Bertkau ('82) found 500 in the undivided cribellum of Dio- Fig. 142. THE TIP OF THE ABDOMEN ,. , , o • u u if of loxosceles c, coiuius hma and about 4800 in each half of the cribellum of Stegodyphus lineatus, making 9600 in all. Or, to select observations based upon genera represented in the United States, Bertkau found over 300 spinning tubes in each half of the cribellum of a Dictyna, and about 3600 in the undivided cribellum of an Uloborus. It is evident that the threads issuing from the spinning tubes of the cribellum are ex- ceedingly small. These threads are used, doubtless, in the forma- tion of a part of the hackled band which is a characteristic feature of the webs of spiders possessing a cribellum and a calamistrum. The Colulus (col'u-lus). — Immediately in front of spin- nerets there is in certain spiders a slender or pointed appendage, the colulus (Fig. 142, c). The function of this organ is unknown. It is wanting in the tarantulas, the Drassidae, and those families in which the cribellum exists. It has been suggested by Menge that the colulus is the homologue of the cribellum. The Anus. — The posterior opening of the alimentary canal is situated just behind the group of spinnerets, on the lower side of the last segment of the postabdomen. The Stridulating Organs. — In some of the comb-footed spiders, Theridiidae, the males possess a stridulating organ, con- sisting of a scraper on the abdomen and a file on the thorax; this organ is described in the account of that family. Stridulating organs borne by the mouth-parts are described on page 2f 136 OS w Q Oh Q w o 6 < fa O § o H < < fa K H fa O < os o < fa CHAPTER III: THE INTERNAL ANATOMY OF SPIDERS The more general features of the internal anatomy of spiders are illustrated by the accompanying plate (Fig. 143) upon which the different systems of organs are indicated by different colours, except that the muscles and the endosternites are omitted, in order that the diagram should not be too complicated. This plate represents the organs projected upon a vertical, median section of the body. The black outline of the figure represents the body-wall; the respiratory organs which are, morphologically, infoldings of the body-wall, are indicated by the same colour; the alimentary canal is coloured yellow; the blood vascular system, red; the nervous system, blue; the poison gland, the silk glands, and the Malpighian vessels, green; and the reproductive organs, purple. THE BODY-WALL a. THE THREE LAYERS OF THE BODY-WALL In that division of the Animal Kingdom to which spiders belong, the phylum Arthropoda, the outer covering of the body serves as a skeleton as well as a protecting shield. It is more or less firm in texture, and to its inner surface and to inward projections of it are attached the muscles that serve to move the body and its appendages; and within the cavity bounded by it are located the viscera. In other words, the body-wall is a firm tube containing the softer structures. The appendages of the body, that is, the legs, the mouth-parts, and the spinnerets, are also tubular, and the cavity of each communicates with the general body cavity. Three, more or less distinct, layers can be recognized in the body-wall of a spider; first, the outer protecting layer, the cuticula; second, an intermediate cellular layer, the bypodcrmis; and third, an inner, delicate, membranous layer, the basement membrane. 137 The Internal Anatomy of Spiders As the outer and inner layers are derived from the hypodermis, it will be described first. The hypodermis. — The hypodermis is the active, living part of the body-wall. It consists of a single layer of cells (Fig. 144, by). Certain of the hypodermal cells become highly specialized and produce the hollow hairs with which the body is clothed; such a hair-forming cell is termed a trichogen (Fig. 144, tr), each trichogen remains connected through a pore in the cuticula, the trichopore, with the cavity of the hair it produces. Other hypodermal cells are modified so as to form glands, which open through pores in the cuticula, either directly or through the tubular hairs. These glands may be either unicellular or multicellular. The cuticula. — Outside is a firm layer, which pro as a support for the inter cuticula. The cuticula con an outer, usually thinner, pigments that produce the of the hypodermis, there tects the body and serves nal organs; this is the sists of two layers: first, layer, which contains the colours of the outer sur- Fig. 144- DIAGRAM OF A SECTION OF THE BODY-WALL cu.i, primary cuticula at. 2, secondary cuticula hy, hypodermis bm, basement membrane tr, trichogen s, seta tp, trichopore face, the primary cuticula (Fig. 144, cu. /); and second, an inner, usually thicker, layer, devoid of pigment, the secondary cuticula (Fig. 144, cu. 2). The secondary cuticula is laminate; the laminae remind one, when the cuticula is seen in section, of the lines of growth of an exogenous tree. The well-known firmness of certain parts of the body-wall is due to the presence in the cuticula of a substance which has been termed chitin. This substance bears some resemblance in its physical properties to horn; but it is very different from horn in chemical composition. \^ The Internal Anatomy of Spiders When freshly formed, as is done before each moult, the cutio ula is flexible and elastic, and certain portions of it, as at the nodes of the body and of the appendages, and throughout the greater part of the wall of the abdomen in spiders, remain so. But the greater part of the cuticula of the cephalothorax and of the appendages becomes firm and inelastic; this is probably due to a chemical change resulting in the production of chitin. What the nature of this change is or how it is produced is not yet known; but it is evident that a change occurs; we may speak, therefore, of chitinifed cuticula and of non-chitini{ed cuticula. The hinge-like movements of the body and of the appendages are made possible by the non-chitinized condition of the cuticula at the joints. A portion of the body-wall that is sharply distinguished from surrounding portions by being chitinized is called a sclerite; and a narrow line between two sclerites is termed a suture. I he basement membrane. — The inner ends of the hypodermal cells are bounded by a very delicate, but more or less distinct, membrane, the basement membrane (Fig. 144, bm). b. THE CUTICULAR APPENDAGES Under the head of cuticular appendages are included those outward prolongations of the body-wall that do not form an in- tegral part of it, being separated from it, in each case, by a flexible joint; such appendages are the hairs or setae and the movable spines. The fixed spines, as for example those borne by the abdomen of Micrathena (Fig. 145), are not re- garded as appendages. These form an integral part of the body-wall and differ only in size from mere nodules on the surface of the body. The hairs or setcr.- — These vary greatly in their external form; but no distinction, except in degree of stiffness, can be made between the extremely slender and very flexible type commonly called hairs and the stiffer one commonly Fig. 145. MICRATHENA 139 The Internal Anatomy of Spiders n. Fig. 146. SECTION OF A SETA n, nerve (after Hilton) Fig. 147. GLANDULAR HAIR OF A CATERPILLAR (after Hilton) termed setae; the two are morphologically the same, and they grade by insensible degrees into each other. As regards their internal structure, the hairs of spiders, like those of insects and other arthropods, differ markedly from the hairs of mammals, being hollow. Each hair of a spider arises from a more or less cup-like cavity in the cuticula of the body-wall, which may be made more pronounced by a ring-like elevation of the cuticula surrounding it (Fig. 144); but the latter feature is not an essential one. The sheath of the hair is con- tinuous with the cuticula of the body-wall, but at its base it is infolded and more or less flexible, thus forming the joint. The cup-like cavity in the cuticula from which the hair arises is situated at the end of a pore in the cuticula, the trichopore. The trichopore and the base of the hair is filled with a prolongation of the hypo- dermal cell that formed the hair, the trichogen (Fig. 144, tr). The above may be regarded as the essential features of an arthropod hair. Certain writers refer to protecting hairs, which are supposed to present only these features, and to serve merely to protect the body. My own observations, based, it is true, chiefly on the hairs of insects, lead me to doubt the existence of hairs that are merely protective in function. In most cases, if not in all, each hair is supplied with a minute nerve, connecting the hair with a subhypodermal nerve plexus (Fig. 146); this feature has been carefully worked out with insects, and it is not probable that it is radically different in spiders. Hairs furnished with a nerve are regarded as organs of special sense; in most cases they are organs of touch, the tactile hairs; these are discussed later. A very important modification of the ordinary type of a hair is that known as the glandular hair. These are hairs that serve as outlets of hypodermal glands (Fig. 147); several kinds of these, that are found in insects, have been described. The 140 The Internal Anatomy of Spiders type of glandular hair that interests most the student of spiders is that known as the tenent hairs. These are found on the terminal segments of the legs and serve to aid in walking. For figures of tenent hairs see page 124. C. THE ENDOSKELETON In the Arthropoda, as already stated, the outer covering of the body serves as a skeleton as well as a protecting shield; but in addition to the firm outer layer of the body-wall, there are found, within the body-cavity certain hard parts which serve for the attachment of muscles; these constitute the endoskeleton. The presence of these parts that constitute the endoskeleton forms only an apparent exception to the statement that the body-wall constitutes the skeleton; for these parts are merely infolded portions of the body-wall. The apodemes. — The infoldings of the body-wall that serve for the attachment of muscles vary greatly in form; they may be merely a slight ridge or they may be a prom- inent projection into the body cavity. In the latter case such a projection is termed an apodeme. The endosternites. — In the ce- phalothorax of spiders there is a horizontal plate above the ventral ganglion and below the alimentary canal, to which many muscles are attached. This is known as the endojternite; but as there are endosternites in the abdomen also, it may be specifically desig- nated as the endosternite of the cephalothorax (Fig. 148). The question of the origin of this endosternite has been much discussed; but it has been shown by Bernard ('96) that it is formed by the fusion and expansion of the tips of four pairs of apodemes, a pair extending into the body cavity in front of each pair of legs. The position occupied by these apodemes is that of the original intersegmental spaces, vestiges of which remain as lines across the sternum in very young spiders. The endosternite is, therefore, a part of the body-wall, like the more simple apodemes. Fig. 148. THE EXDOSTERNITE OF THE CEPHALOTHORAX OF ARANEA (after Schimkcwitsch) 141 The Inter nal Anatomy of Spiders The endosternites are termed aponeurotic plates by sorru writers, who believe that they are formed by the coalescence of the tendons of muscles. A so-called aponeurotic plate, which occurs in the pedicel of the abdomen, has been described. This, however, occupies a very different position from that of the endosternites, being near the dorsal body-wall above the aorta. The source of this plate has not been determined. In the sac-like portion of the abdomen, there are vestiges of an endoskeleton. These vestiges are three centres of attach- Fig. 149. THE THREE ABDOMINAL ENDOSTERNITES AND THE PRINCIPAL MUSCLES ATTACHED TO THEM en 1, en 2, en 3, first, second, and third abdominal endosternites (after Schimkevvitsch) ment of muscles, one opposite the epigastric furrow, one a short distance back of this, and one near the furrow of the posterior spiracle (Fig. 149, en 1, en 2, en 3); these may be designated as the first, second, and third abdominal endosternites respectively. The endosternites of the sac-like part of the abdomen are described by authors as intermediary tendons; but it seems clear to me that they are serially homologous with the endosternite of the cephalothorax. Correlated with the loss of the abdominal appendages there has been a reduction of the connection of the endosternites with the body-wall. THE MUSCULAR SYSTEM A striking feature of the muscles of spiders, and also of other arthropods, is the distinctness of the muscular fibres; each muscle being composed of a number of distinct, more or less isolated, straight fibres; and the fibres constituting a muscle are not enclosed in a common tendinous sheath, as is the case with vertebrates. 142 The Internal Anatomy of Spiders In appearance the muscles are either colourless and trans- parent, or yellowish white; and are of a soft, almost gelatinous consistence. When properly treated with histological reagents, and examined with a microscope of moderately high power, they present numerous transverse striations, like the voluntary muscles of vertebrates. Unstriped muscles are rare with arthropods; certain muscles, which have been supposed to be unstriped, show striations when properly treated. The chief muscles are attached to the inner surface of the body-wall, to infoldings of it, the apodemes, and to the endo- sternites described in the preceding section. There are also prominent muscles attached to the alimentary canal, especially to the sucking stomach (Fig. 150). It is not within the province of this book to enter into a de- scription of the separate muscles; there is space for only a few general statements. The muscles of the cephalo- thorax are extremely well devel- p.g ijo ^TRAM 0F A oped; while those of the abdomen transverse section of the are ereatlv reduced This is ror- cephalothorax showing are greatly reduced. 1 nis is cor- THE PRINCIPAL muscles related, to a considerable extent, (after Schimkewitsch) with the greater number and size of the appendages of the cephalothorax, the appendages of the abdomen, excepting the spinnerets, having been lost, and to the presence in the cephalothorax of a powerful sucking stomach. The muscles of the body-wall. — The muscles of the body-wall, which form the most prominent feature of the muscular system of the larvae of insects that are commonly studied, are very greatly reduced in spiders. This is doubtless due to the fact that the segments of the cephalothorax are fused in spiders so that there can be no movements between them, and that the abdomen is practically unsegmented. There are present, however, ves- tiges of both circular and longitudinal "skin-muscles." The muscles of the appendages. — A very large proportion of the muscles of the cephalothorax serve to move the appendages. Some of these have their origin on the inner surface of the body- wall and others, on the endosternite; in each case they extend 143 The Internal Anatomy of Spiders to the basal segment of the appendage. There are also muscles within the appendages that produce the movement of the separate segments of the appendages. Figure 151, which represents the musculature of a leg of Thelyphonus, one of the Pedipalpida, will serve as an illustration of the arrangement of the muscles in the leg of an arachnid. The muscles of the sucking stomach. — The muscles of the sucking stomach are also very prominent; these are discussed in the section of this chapter treating of the alimentary canal. The muscles of the abdomen. — It is much more difficult to trace out the muscles of the abdomen than it is those of the cephalothorax. In the abdomen the muscular system is greatly reduced and other viscera are so greatly developed that the muscles are overshadowed by them. Schimkewitsch ('84) gives a diagram showing the arrangement of the principal muscles of the abdomen of Aranea (Fig. 149). In this figure are represented the three vestiges of the endoskeleton of the sac-like part of the abdomen (Fig. 149, en 1, en 2, en 3,); these I have des- ignated as the first, second, and third abdominal endosternites re- spectively. The most prominent of the muscles of the abdomen is a series extending from the pedicel of the abdomen to the three endosternites successively and from the third endosternite to the spinnerets. These have been named the longitudinal ventral muscles. From the second and third endosternites there extend two pairs, one from each, of dorsoventral muscles. These are the muscles that are attached to the two pairs of more prominent muscle impressions, that appear externally as depressed points in the dorsal wall of the abdomen. To the first abdominal endosternite are attached in addition to the longitudinal muscles, muscles from the book-lungs, and a muscle from the opening of the reproductive organs. To the second abdominal endosternite are attached several muscles extending to the body-wall. Fig. 151. THE MUSCLES OF A LEG OF THELYPHONUS (after Borner) 144 The Internal Anatomy of Spiders The muscles extending backward from the third abdominal endosternite are those that move the spinnerets. THE RESPIRATORY ORGANS In the order Araneida, two types of respiratory organs are found; first, the book-lungs; and second, the tubular tracheae. Some members of the order possess only one of these types; but the greater number of spiders possess both. The number of respiratory organs is reduced in spiders to two pairs; and in most true spiders the second pair open by a single spiracle on the middle line of the body. The more generalized spiders preserve two pairs of book-lungs. This condition is retained by Liphistius, all of the tarantulas, and by a single family of the true spiders, the Hypochilidae. Excepting the Hypochi- lidae, most true spiders have a single pair of book-lungs; but in the Caponiidae, which is not represented in the United States, both pairs of respiratory organs have been transformed into tubular tracheae. The accompanying figures (Fig. 152, 1-4) show in a diagrammatic way the dis- tribution of the two types of respiratory organs among the families of spiders; in these figures the tracheal spiracles can be distinguished from lung-slits by the absence of external indications of book-lungs. The distribution is as follows: 1. With two pairs of book-lungs; Liphistius, the tarantulas (Avicularioidea), and the Hypochilidae. 2. With one pair of book-lungs and one pairof tracheal spiracles; the Filistatidae, the Oonopidae, and the Dysderidae. 3. With one pair of book-lungs and a single tracheal spiracle; all true spiders (Argiopoidea) except the Hypochilidae, Filistatidae, Oonopidae, Dysderidae, and Caponiidae. 4. With two pairs of tracheal spiracles; the Caponiidae. The hook-lungs. — These are sacs filled with air each of which open by a slit-like spiracle on the ventral aspect of the abdomen Fig. 152. DIAGRAMS SHOWING THE DISTRIBUTION OF THE TWO TYPES OF RESPIRATORY ORGANS 1, Liphistius, the taran- tulas,and Hypochilidae 2, Filistatidu.-. Oonopidae, and D : rid 3, all true spiders except the five families men- tioned here 4, Caponiida: 145 The Internal Anatomy of Spiders near its base. Their position is indicated externally on the living animal as pale trapezoidal spots with rounded angles (Fig. 153). The first pair open, one on each side, in the epigastric furrow; when there is a second pair they open a short distance back of the first pair. From the anterior wall of each sac there project a series of horizontal, leaf-like folds, which has suggested the name of book- 1 Fig. IS3- VENTRAL ASPECT OF THE ABDOMEN OF A TARANTULA Fig. 154- DIAGRAM OF A BOOK-LUNG 1 , lung-slit 2, space filled with blood 3, leaves of the book -lung lungs (Fig. 143). But as these leaves are also attached to the lateral walls of the sac, the lung has been more aptly compared to that form of a letter-file that consists of an envelope divided by manypartitions into numerous compartments (Lang '91). Each leaf of the book- lung consists of a flattened, sac-like fold of the body-wall, and hence of two lamellae. These lamellae are connected at frequent intervals by ver- tical supports; and the leaves are kept apart, so that the air can circulate between them, by a palisade of vertical, knobbed spines on the upper surface of each (Fig. 154). At and near the free edge of the leaves, these spines are longer, and, instead of being knobbed, divide at the tip into several branches, which anastomose with branches of adjacent spines (Fig. 155). 146 Fig. 1 ss. THE TIPS OF TWO LEAVES OF A BOOK-LUNG i,i, palisade of spines on dorsal lamella 2, vertical support between lamellae contracted 3, vertical support stretched 4, blood-cavity 5, globule of blood (after Bcrteaux) The Internal Anatomy of Spiders The blood passes from the body-cavity into the lumen of each leaf, and the respiratory process takes place through the walls f the leaves. A hint regarding the mode of origin of this highly specialized respiratory apparatus is afforded by the comparatively simple lung-sacs of the Microthelyphonida, referred to on page 13. The tubular trachea. — The distribution of tubular tracheae among the different families of spiders, and the number of tracheal spiracles are indicated by Fig. 152. In most cases the tracheae open by a single spiracle, situated on the middle line of the ventral aspect of the abdomen; sometimes this spiracle is near the middle k. Fig. 156. TUBULAR TRACHE/E OF ANYPH.ENA (after Bertkau) Fig. IS7- SECTION OF HEART AND PARTS LYING ABOVE IT (after Vogt et Yung) of the length of the abdomen, but usually it is only a short dis- tance in front of the spinnerets. In a few spiders there is a pair of tracheal spiracles situated just behind the lung-slits. These can be distinguished from lung-slits by the absence of external indications of book-lungs. The tracheae are paired organs even when they open by a single spiracle; this is well-shown by the figure of the main trunks of the tracheae of Anyphana (Fig. 156). As to the histological structure of the tracheae, they, like the tracheae of insects described in many text-books, present the same layers as does the body-wall, namely, a chitinous intima lining the cavity and continuous with the cuticula of the body-wall; an epithelial layer surrounding 147 The Internal Anatomy of Spiders this and continuous with the hypodermis; and, bounding the epithelium next to the body-cavity, a basement membrane, continuous with the basement membrane of the body-wall. As with insects the chitinous intima is thickened spirally. The ramifications of the smaller tracheal branches appear to be much less extended than are the tracheae of insects; this is probably due to the book-lungs being the chief organs of respiration. THE CIRCULATORY SYSTEM The circulatory system of spiders is an incomplete one; that is, for only a portion of its course does the blood flow in blood-vessels; during a part of its course it enters the body- cavity, as is the case with insects, where it fills the space not occupied by the internal organs. The extent of the vascular system, however, is much greater with spiders than it is with insects. The heart.- — The heart resembles the heart of an insect in position, being situated in the abdomen a short distance within the middle line of the dorsal body-wall, and above the intestine. In many spiders it is sunken to a greater or less depth in the mass of alimentary tubules; it is then difficult to expose it by dissection. Its position is represented in Fig. 143; and in Fig. 157 are represented some details not shown on the coloured plate. In this figure, a, represents the body-wall; b and c, a lobe of the ali- mentary tubules, of which b is the chalky layer; d, the dorsal longitudinal venous sinus; e, the pericradium, to be described later;/, the pericardial cavity; g, the longitudinal muscular layer of the heart; h, the annular muscles of the heart; and k, a cardiac ligament. The wall of the heart is composed of three distinct layers: an inner, very delicate, structureless intima; an intermediate muscular layer; and an outer, connective tissue layer. The intima is so delicate that it is usually difficult to demonstrate its presence. The muscular layer consists chiefly of annular muscles; but there are also longitudinal fibres. The connective tissue layer is composed of slender fibres between which elongated nuclei can be seen. The heart in spiders is a simple tube not divided into chambers by valves, as is the heart of insects. 148 The Internal Anatomy of Spiders The more general features of the heart of different types of spiders are represented diagrammatically by the drawings in Fig. 1 58, which are based on a series of figures given by Causard ('96). The first drawing (1) represents the heart of a four-lunged spider; the second (2), the usual form of the heart in the two- lunged spiders; and the third (3), the heart of Dysdera. The I 2 3. Fig. 158. DIAGRAMS OF HEARTS OF SPIDERS (after Causard) heart is somewhat enlarged toward the anterior end and tapers toward the posterior end. From the anterior end extends the aorta (a); from the posterior end, the caudal artery (ca);and from its sides, the lateral abdominal arteries (la). The cavity of the heart is more or less expanded at regular intervals, forming paired diverticula, from which the arteries arise. The wall of the heart is pierced by a series of paired openings, the ostia From the heart extend a considerable number of strands, the cardiac ligaments (cl). At some distance from the heart, but 149 The Internal Anatomy of Spiders completely surrounding it, is a thin-walled sac, the pericardium (p). Between the pericardium and the heart is the pericardial cavity (pc). The first one or two pairs of cardiac ligaments are larger than the others and function as pulmonary veins (pv). Each of the above-mentioned parts is described more in detail below. The ostia of the heart. — The wall of the heart is pierced by several pairs of openings by which the blood is received into the heart; these are the ostia (Fig. 158, o). In the four-lunged spiders there are four pairs of ostia (Fig. 158, 1); in most of the two-lunged spiders there are three pairs (Fig. 158, 2); but in some of the two-lunged spiders, as in Dysdera (Fig. 158, 3), the number is reduced to two. The diverticula of the heart. — As indicated above, the cavity of the heart is more or less expanded at regular intervals; and these expansions form paired diverticula. In the more generalized spiders, six pairs of these diverticula can be recognized. The four pairs of ostia of the heart in these spiders are in the walls of the first, second, third, and fifth pairs of diverticula respectively (Fig. 158, 1); the fourth pair of diverticula are midway between the third and fourth pairs of ostia, and bear only vestigial liga- ments; the sixth pair is near the caudal end of the heart. In more specialized spiders the number of diverticula is more or less reduced; those which are most constantly prominent are the first, third, and fifth pairs, in the walls of which are the three pairs of ostia characteristic of most two-lunged spiders; the sixth pair are also usually well-marked, as from them arise a pair of arteries. The aorta. — The aorta (Fig. 1 58, a) is the forward prolon- gation of the heart. It extends through the pedicel of the abdo- men into the cephalothorax (Fig. 143). As it enters the cephalothorax, it gives off some small branches which ramify among the muscles of the posterior part of the cephalothorax. It then extends forward to a point near the sucking stomach, where it divides into two trunks, one passing forward on each side between the sucking stomach and the caecal ring. Each of these trunks sends branches to the appendages, to the eyes, to the muscles, and to other organs of its side. This account of the course of the branches of the aorta is based on the figures and descriptions given by Causard ('96) and those by Petrunkevitch 150 The Internal Anatomy of Spiders ('10 b). It differs markedly from that commonly given in the text-books of zoology. The lateral abdominal arteries. — In the four-lunged spiders, there are four pairs of lateral abdominal arteries; these extend from the second, third, fifth, and sixth pairs of diverticula (Fig. 158, 1, la). In the two-lunged spiders, the first of these four pairs is lacking (Fig. 158, 2); and in Dysdera, the first and second pairs are lacking and the third is greatly reduced in size (Fig. 158, 3). The caudal artery. — The caudal artery is the backward pro- longation of the heart (Fig. 158, ca). It divides into many small branches, which supply blood to the spinnerets and to the abdominal viscera. The pericardium. — At some distance from the heart, but completely surrounding it is a thin-walled sac, which is termed the pericardium (Fig. 158, p). The space between the pericardium and the heart is the pericardial cavity (Fig. 158, pc). The cardiac ligaments— -The heart is supported by a con- siderable number of ligaments. These extend from the heart to the body-wall; some of them extend dorsally, some ventrally, and some laterally. In Fig. 158, only the laterally extending ligaments are represented. In Fig. 157 a dorsally extending ligament (k) is shown; and several of them are represented in Fig. 143. The laterally extending cardiac ligaments are termed, by some writers, the alary muscles, by analogy with the "wings of the heart" of insects. But Causard ('96) has shown that the cardiac ligaments are not muscles, but are formed of connective tissue. Each cardiac ligament is formed by a bundle of connective tissue fibres, which is inserted in the heart, and is enclosed in a tubular prolongation of the pericardium (Fig. 158, cl). The cardiac ligaments that extend laterally have been designated the exocardiac ligaments; those that extend dorsally, the epicardiac ligaments; and those that extend ventrally, the hypocardiac ligaments. 1 he pulmonary veins. — In the basal part of the abdomen of the four-lunged spiders, there are two pairs of large vessels which convey the blood from the two pairs of book-lungs to the pericardial cavity; and in the two-lunged spiders, there is a single pair of these vessels; these are the pulmonary veins (Fig. 158, pv). 151 The Internal Anatomy of Spiders According to Causard, the pulmonary veins are large hollow exocardiac ligaments, which serve as veins in addition to their function of holding the heart in place. In fact he regards the other exocardiac ligaments as reduced pulmonary veins, which have lost their venous function, and become merely ligaments. The venous circulation. — From the arteries the blood passes into the spaces of the body-cavity between the viscera, bathing the various organs. It then passes into two longitudinal sinuses, one dorsal and one ventral, which lead to the base of the abdomen. Here it is purified by the book-lungs; and then it passes through the pulmonary veins to the pericardial cavity, from which it enters the heart through the ostia. The blood is also purified to a greater or less extent by tubular tracheae as it is in insects; but the extent of the ramifications of these tracheae varies greatly in different spiders. THE ALIMENTARY CANAL The alimentary canal of arthropods is a tube extending from one end of the body to the other. With some arthropods, as the larvae of insects, it is a nearly straight tube; with others, as most adult insects, it is greatly lengthened, being much longer than the body and, consequently, more or less coiled within it. This increase in the length of the alimentary canal gives an increased surface for the performance of its functions. In spiders, and other arachnids an extended area of the digestive tract is obtained in a different and peculiar manner; instead of a lengthening of the intestine, there have been de- veloped extensive diverticula, extending in different directions from it (Fig. 143). Three chief regions of the alimentary canal are recognized; namely, the fore-intestine, the mid-intestine, and the hind- intestine. These regions differ in their histological structure, a difference due to different embryological origin. The fore- intestine and the hind-intestine are developed from an infolding in each case of the ectoderm, the germ layer from which the body- wall is formed. And these regions are lined with a chitinous layer, the intima, which is a continuation of the cuticula of the body-wall. On the other hand, the mid-intestine is developed from the entoderm and is lined by an epithelium. 152 Fig. 159. SECTION OF WALL OF SUCKING STOMACH The Internal Anatomy of Spiders The fore-intestine is that portion of the alimentary canal that is developed from an infolding of the ectoderm at the anterior end of the embryo, the stomodceum. It consists of the pharynx, the oesophagus, and the sucking stomach. The histological structure of the fore-intestine is the same as that of the body-wall; the lumen being lined with a chitinous intima, a continuation of the cuticula; and, surrounding this, there is an epithelial layer, continuous with the hypodermis; and this in turn is bounded on the side toward the body-cavity by a basement mem- brane. The muscular coat of the fore-intestine, which is well-marked in some arachnids, is absent in the true spiders. Figure 1 59 represents a small portion of the wall of the sucking stomach, in this the layers are shown and also the attachment of some muscles. The pharynx. — The pharynx or mouth-cavity is situated between the rostrum and the sternum. It extends in a more or less nearly vertical direction (Fig. 143). It is bounded in front by a plate borne by the rostrum, which may be termed, by an analogy drawn from the anatomy of insects, the epipharynx; and is bounded behind by a plate borne by the sternum, which by a similar analogy may be termed the hypopharynx. By bringing together the lateral margins of the epipharynx and the hypopharynx, a tube-like cavity is formed into which the spider sucks the juices pressed from its prey by the mouth-parts, the tufts of hairs borne by the mouth-parts preventing the escape of the liquid food. The epipharynx is marked by many transverse striae (Fig. [60) which lead to a longitudinal slit in its middle line, which in turn leads to the opening of the oesophagus. Thus if the mOUth- Fig. 160. THE EPIPHARYNX '53 The Internal Anatomy of Spiders cavity be closed as tightlyas possible bythe pressing togetherof the epipharynx and the hypopharynx there will still remain an open way for the passage of the last drop of fluid pressed from the prey. At the upper end of the pharynx near the entrance to the oesophagus there is a straining apparatus consisting of hairs which prevent the entrance of solid food into the oesophagus. Several pairs of muscles extend from the walls of the pharynx to the body-wall; one of these, the retractor of the pharynx, is attached to the upper end of the pharynx and is sometimes very large. Within the ros- trum there is an unpaired gland, the pharyngeal gland, which opens into d- the pharynx near the beginningof the oesophagus. The (Esopha- gus.— This is that part of the fore- intestine that con- nects the pharynx with the sucking stomach; it extends in a more or less nearly horizontal direction and con- sequently nearly at right angles to the pharynx. It is tubular in form; and the intima of its dorsal and lateral walls is thick and strong, forming an inverted gutter-like sclerite, which is transversely striated. The epithelium of the oesophagus is greatly reduced. The hind portion of the oesophagus is sur- rounded by the central nervous system; the course of this part of it is indicated in Fig. 143 by dotted lines. The sucking stomach— -The sucking stomach is an enlarged portion of the fore-intestine, whose function is indicated by its Fig. 161. CROSS-SECTION OF THE SUCKING STOMACH AND ADJACENT PARTS a, dorsal plate b, lateral plate c, ventral plate d, endosternite ee, sphincter muscles (after Vogt et Yung) 154 The Internal Anatomy of Spiders name. It is situated just behind the point where the fore- intestine emerges from the nervous collar and rests upon the endo- sternite (Fig. 143). The chitinous intima of the fore-intestine is greatly thickened in this region, affording a firm support for powerful muscles. In a cross-section of the sucking stomach (Fig. 161), it can be seen that the thickened intima consists of four longitudinal plates; a dorsal and a ventral one, and one on each side. From the dorsal plate very strong muscles extend to the ental surface of the median furrow of the cephalothorax; and from the ventral and the lateral plates muscles extend to the endosternite. These act to enlarge the cavity of the organ. Opposed to the muscles just described, the sucking stomach is supplied with sphincter muscles (Fig. 161). These it will be observed are outside of the wall of the intestine and do not, therefore, strictly speaking, form a muscular coat of the intestine. b. THE MID-INTESTINE The mid-intestine begins a short distance back of the sucking stomach; it differs greatly from the fore-intestine both in histo- logical structure and in general form. The distinctively characteristic feature in the structure of the mid-intestine is the absence of a chitinous intima; this portion of the alimentary canal being lined with a layer of cells, the essen- tial digestive element of the organ (Fig. 162, ep). This digestive epithe- lium rests on a basement membrane, outside of which there is a peritoneal layer composed of fibres, presumably of connective tissue (Fig. 162, p). No muscular coat has been observed; but . , , . . . . . Fig. 162. CROSS-SECTION OF outside of the peritoneal layer there mid-intestine (after Bertkau) is a cellular layer, which has been termed by several writers, but 1 believe incorrectly, a peritoneal layer (Fig. 162, f). This so-called peritoneal layer, I believe to be the fat-bodv, which is described later. The most striking feature of the mid-intestine of spiders is the presence of an extensive system of diverticula by means of which the extent of the digestive epithelium is greatly augmented. In the cephalothorax, these diverticula are in the form of large •55 The Internal Anatomy of Spiders simple caeca; but in the abdomen they are much-branched tubules, forming a great mass, which has the general appearance of a gland. These diverticula may be designated as follows: The anterior cceca. — At the beginning of the mid-intestine a caecum extends forward on each side of the dorsal muscle of the sucking stomach (Fig. 163 ac). These two caeca often unite in front of this muscle, thus forming what has been termed the ring- stomach, or the ccecal ring. The lateral cceca. — From each anterior cae- cum, four lateral caeca arise. These extend later- ally and ventrally and each ends in or near a coxa of a leg (Fig. 163, Ic). The alimentary tubules. — In the anterior part of the abdomen, there arise, from a somewhat ex- panded portion of the mid-intestine, several much-branched dorsal di- verticula; these constitute the alimentary tubules. These are developed to such an extent that they form the most prominent part of the viscera of the abdomen. The mass of alimen- tary tubules was described by the early writers as the liver and by later ones as a digestive gland; but it has been shown that the epithelium of these tubules does not differ from that of the main portion of the mid-intestine; and that the food penetrates to the tips of the tubules and is absorbed by the tubules. C THE HIND-INTESTINE The hind-intestine is the terminal portion of the alimentary canal; it is that part that is developed from an infolding of the 156 Fig. 163. DORSAL VIEW OF THE CEPHALOTHORACIC PORTION OF THE ALIMENTARY CANAL 0, oesophagus s, sucking-stomach ac, anterior caeca, united in front Ic, lateral caeca (after Leuckart) The Internal Anatomy of Spiders ectoderm at the posterior end of the embryo, the proctodeum. It, consequently, like the fore-intestine, resembles the body-wall in its histological structure, there being a chitinous intima, an epithelial layer and a basement membrane. It differs from the fore- intestine in possessing a more or less well-developed muscular coat. The stercoral pocket. — The most striking feature of the hind- intestine is the presence of a large, bladder-like diverticulum of its dorsal wall, which is situated near the place of union of the mid-intestine and hind-intestine (Fig. 143). It serves as a res- ervoir of fecal matter and is termed, therefore, the stercoral pocket (ster'co-ral). The Malpighian vessels. — There is a pair of tubes which open into the alimentary canal near or at the place of union of the mid-intestine and hind-intestine; these are the Malpighian vessels (Mal-pe'ghi-an or Mal-pig'hi-an). Each of these tubes is branched and the branches ramify among the alimentary tubules. They are supposed to correspond to the kidneys in function. Some writers maintain that Malpighian vessels open into the mid-intestine. If this should prove to be true, they cannot be homologous with the Malpighian vessels of insects, which are developed from the proctodeum. The rectum. — The rectum is a simple tube extending from the stercoral pocket to the anus. THE ADIPOSE TISSUE In spiders the greater part of the adipose tissue or fat-body is intimately associated with the mid-intestine and its diverti- cula. In the case of the simple caeca of the mid-intestine, situated in the cephalothorax, the fat cells form a continuous investing sheath, which has been termed, incorrectly, the peritoneal coat. In the abdomen, the fat-body completely fills the spaces between the alimentary tubules, and surrounds them as a whole. In many spiders the fat-body presents a chalky appearance due to the presence in it of fine particles, which are believed to be crystal-like remains of the food. These "fecal crystals" are sometimes very abundant in the dorsal superficial portion of the mass; and, showing through unpigmented portions of the cuticula, produce conspicuous white markings. 157 The Internal Anatomy of Spiders In the cephalothorax, between the nervous system and the body-wall, there is a layer of fat cells which appear to perform a function similar to that of the urate cells of insects. THE REPRODUCTIVE ORGANS The two sexes are distinct in all Arachnida; and in each sex, the reproductive organs lie in the abdomen, and open near its base. a. THE REPRODUCTIVE ORGANS OF THE MALE The testes and their ducts. — The testes are situated in the anterior part of the abdomen, between the ventral body-wall and the longitudinal ventral muscles. They are two long tubes (Fig. 164, /); which are closed behind, and are continued in front as two, long, thin, and often much coiled sperm ducts, the vasa defer entia (Fig. 164, vd). The two vasa deferentia open into a common pouch, the seminal vesicle (Fig. 164, sv); and the seminal vesicle opens in turn through a single opening on the middle line of the body in the epigastric furrow. The palpal organ. — There is no copulatory organ directly connected with the outlet of the reproductive glands; but the seminal fluid is transferred to the female at the time of the pairing of the sexes by means of a highly specialized appendage of the palpus of the male. This organ is described in detail in the preceding chapter. b. THE REPRODUCTIVE ORGANS OF THE FEMALE The internal reproductive organs of the female consist of the ovaries, the oviducts, the uterus, the vagina, and one or more pouches for the reception of the seminal fluid at the time of pair- ing, the spermathccce. The vagina and the spermathecae are invaginations of the body-wall and, like other invaginations of the body-wall, are lined with a chitinous intima, which is a con- tinuation of the cuticula; while the uterus is lined with an epithe- lium similar to that lining the oviducts. .58 Fig. 164. DIAGRAM OF THE REPRODUCTIVE ORGANS OF THE MALE /, testes 8 d, vasa deferentia s v, seminal vesicle (after Bertkau) The Internal Anatomy of Spiders In certain generalized spiders, as Atypus, Segestria, Dysdera, Tetragnatha, and others, the spermathecae are diverticula of the vagina. In these cases there is only a single external opening of the reproductive organs. But in most spiders, the sperma- thecae are more or less detached and have separate external openings. In these cases there are three external openings of the repro- ductive organs, the opening of the vagina, and a pair of openings of the afferent ducts leading to the sper- mathecae. In this type of reproductive organs, a tube connects the sperma- thecae of each side with the vagina. Figure 165 is a diagrammatic repre- sentation of this type. The ovaries. — The ovaries are situ- ated in the abdomen below the intes- tine and above the longitudinal ventral muscles (Fig. 143). They are sur- rounded by silk glands and the ali- mentary tubules, and are two broad tubes bearing numerous ovarian fol- licles and appearing like a cluster of grapes. The free ends of the ovaries are sometimes .grown together so as to pro- duce a ring-like structure (Fig. 166). The size of the ovaries varies greatly, de- pending on the state of the development of the eggs. Just before the egg-laying period, they become greatly distended and occupy a consider- able part of the abdominal cavity. The oviducts. — Each ovary opens through a short oviduct; and these in turn open into a common pouch, the uterus, which leads to the vagina; and the vagina opens on the middle line of the body in the epigastric furrow. The spermatheca:. — The spermathecae vary in number. In those spiders where the sperma- thecae are diverticula of the vagina, as described above, there are, according to Engelhardt ('10), two in Pachygnatha, three Fig. 165. DIAGRAM OF THE INTERNAL REPRODUCTIVE ORGANS OF THE FE- MALE OF ARANEA 0, ovary od, oviduct u, uterus v, vagina s, spermatheca os, opening of the spermatheca 1, tube connecting the spermatheca with the vagina g, gland of the spermatheca ig. 166. RING- LIKE OVARIES OF A SPIDER 0, ovaries od, oviduct s, spermathec (after Lang) 159 The Internal Anatomy of Spiders in Tetragnatha, and five in Segestria; and according to Bertkau ('75) twenty-eight in Atypus. In those spiders where the sperma- thecae are detached there may be either one, two, or three con- nected with the afferent duct of each side. The duct leading from the external opening of a spermathecae to the large reservoir of this organ frequently bears a prominent enlargement with densely chitinized walls (Fig. 165, g). This organ was described by Schimkewitsch ('84), who states that the chitinous layer of its wall is pierced by numerous pores and is surrounded by an epithelium composed of very high cells, which are probably glandular. 1, therefore, propose the term glands of the spermathecce for these organs. As the chitinous wall of these glands is often dark in colour, they may be seen through the body-wall and appear as a pair of dark spots, which may be mistaken for the openings of the spermathecae. The external openings of the afferent ducts of the spermathe- cae are in the epigynum, which is described in the preceding chapter. THE NERVOUS SYSTEM a. THE CENTRAL NERVOUS SYSTEM In fully developed true spiders, the central nervous system is entirely concentrated into the cephalothorax. In early em- bryonic stages there is a pair of ganglia in each segment of the body; but in the course of the embryonic development a cephali- zation of the ganglia takes place which results in their being consolidated into a single mass surrounding the oesophagus (Fig. 143). In the tarantulas, however, there is a small gang- lion in the pedicel of the abdomen. The brain. — That part of the central nervous system that lies above the oesophagus is termed the brain; from it arise the optic nerves and the nerves of the chelicerae. The subcesophageal ganglion. — That portion of the central nervous system lying below the oesophagus is termed the sub- cesophageal ganglion. From this ganglion arise the nerves ex- tending to the pedipalps and those extending to the legs; and from the posterior end extend two large abdominal nerves. The brain and the subcesophageal ganglion are not distinct, as they are in insects, but are consolidated into a single mass surrounding the oesophagus. 160 The Internal Anatomy of Spiders b. THE VISCERAL NERVOUS SYSTEM A visceral nervous system has been proven to exist in spiders and in other Arachnida. It consists of an unpaired nerve con- nected with the brain by paired nerves and running along the oesophagus and stomach. Ganglia connected with the ventral chord have also been described as belonging to the visceral nervous system (Lang). C. THE EYES The number and the position of the eyes have been discussed in the opening pages of the preceding chapter; here we have to do with their internal structure.* The eyes of spiders are o the type known as the several layered ocellus, each eye con- sisting of two or more layers of cells behind a single lens (Fig. 167). The lens (Fig. 167, c) is termed the cornea; the outer of the two more prominent layers (Fig. 167, c. by), the corneal bypodermis; and the inner of these two layers (Fig. 167, r), the retina. The eye is enclosed in a sheath (Fig. 167, ec), the eye- capsule; in some eyes there is a layer of reflecting cells c.hy o.n. e.c. Fig. 167. DIAGRAM OF A POSTBACILLAR EYE c, cornea chy, corneal hypodermis r, retina ec, eye-capsule on, optic nerve (after W'idman) behind the retina, the tapetum; and in some eyes there are pigment cells, which vary in position in different eyes. The cornea. — The cornea or lens of the eye (Fig. 167, c), is merely a modified portion of the cuticula of the body-wall, with which it is continuous. It is a lens-shaped thickening of the cuticula, which is free from hairs and, consequently, is not traversed by trichopores, and in which the primary cuticula is devoid of pigment, permitting the passage of light to the nervous portion of the eye. 'Much has been published regarding the eyes of spiders. The works that I have consulted most in the preparation ot the account given here are the following: Grenacher '70; Graber '8o; Schimkewitsch '84; Bcrtkau '86; W'idman '07; and one. as yet. unpublished paper, l>v Mr (leorge D. Shafer. l6l The Internal Anatomy of Spiders nu. The cornea is moulted and renewed in the same manner as other portions of the cuticula of the body-wall, and at the same time. The corneal hypodermis. — Immediately beneath the cornea is a layer of cells (Fig. 167, c. hy) which is continuous with the hypodermis of the body-wall, and which is merely a more or less modified portion of the hypodermis. Several different names have been applied to this part. It has been termed the vitreous layer, or the vitreum, a term suggested by its analogy with the vitreous hu- mour of the eye of vertebrates; the lentigen, because it produces the lens; and the corneal hypodermis, a self- explanatory term. I prefer the last name notwithstanding its greater length. The retina. — Lying immediately be- hind the corneal hypodermis, is a layer composed of highly specialized visual cells; this is the retina (Fig. 167, r). Each visual cell consists of several parts; there can be distinguished a cell- body, in which there is a nucleus (Fig. 168, nu); the cell-body is con- nected with the central nervous system by means of a nerve-fibre (Fig. 168, nf); and there is also a hard structure, which is known as the optic rod (Fig. 168, rd). The optic rod is the distinctively characteristic feature of a visual cell. The form of this part varies in different eyes, and, sometimes in different parts of the same eye; it is commonly double, occupying two faces of one end of the cell with a thin layer of the cell-body extending between the two elements, but sometimes the two parts are united. As the optic rods of adjacent visual cells are placed side by side, there is a well-marked layer of the retina occupied by the rods; but the position of this layer is not always the same. Two types of eyes are recognized which are distinguished by the position of the nuclei of the retina with reference to the position of the layer of optic rods. In one type the nuclei lie in front of the optic rods or bacilli, as the rods are often termed (Fig. 169); 162 /. 2. Fig. 168. DIAGRAMS OF TWO VISUAL CELLS 1, postbacillar 2, prebacillar nu nucleus nf, nerve fibre rd, optic rod The Internal Anatomy of Spiders the eyes of this type are termed prcbacillar (pre-bac'il-lar) eyes. In the other type the nuclei lie behind the optic rods; such eyes are termed postbacillar eyes. The anterior median eyes are postbacillar; all other eyes of spiders are prebacillar. In the prebacillar eyes (all eyes except the anterior median) the nerve fibres join the visual cells at the end of the cell bearing the rod (Fig. 169); while in the postbacillar eyes (anterior median) the nerve fibres join the visual cells between the nucleus and the rod (Fig. 167). The two types of eyes differ in the method of their develop- ment, but this is a phase of the subject into which we cannot enter here; it is sufficient to state that on account of their peculiar Fig. 160. DIAGRAMS OF A PREBACILLAR EYE c, cornea chy, corneal hypodcrmis r, retina e c, eye-capsule o n, optic nerve «', iris pigment (after Widman) method of development the anterior median eyes are termed by some writers the inverted eyes, while all the other eyes are termed erect eyes. The eye-capsule. — The eye-capsule is a sheath enclosing the eye. It appears to be continuous with the sheath of the optic nerve; it is sometimes termed the post-retinal membrane. The tapetum. — In the eyes of many animals there is a struc- ture that reflects back the light that has entered the eye causing the well-known shining of the eyes in the dark. This is often observed in the eyes of cats and in the eyes of moths that are attracted to our lights at night. The part of the eye that causes 163 The Internal Anatomy of Spiders this reflection is termed a tapetum (ta-pe'tum). The supposed function of a tapetum is to increase the effect of a faint light on the visual organs, the light being caused to pass through the retina a second time when it is reflected from the tapetum, which is behind the retina. The structure of the tapetum varies greatly in different animals; in the cat and other carnivores it is a thick layer of wavy fibrous tissue; in insects it is a mass of fine tracheae; in the Crus- tacea it is formed of a light-coloured pigment in the accessory pigment cells of the eye; and in spiders it consists of a layer of cells behind the retina containing small crystals that reflect the light. The form of the tapetum layer varies in the eyes of different spiders; three types have been described. In the first type it lies immediately within the eye-capsule and encloses the whole of the retina. As the inner end of the eye-bulb is more or less compressed, the tapetum, as Mark has aptly described it in Agelena, is a canoe-shaped structure, with a fissure along the keel, through which the nerves pass to the retina. This type is termed the funnel-form type. The second-type of tapetum is also canoe-shaped, with a slit at the bottom, and is also termed funnel-form; but it differs from the first type in that the funnel is more shallow, enclosing for the most part, only the proximal rod-bearing ends of the visual cells; and it does not lie immediately within the eye-capsule, owing to the fact that the nuclear ends of many of the visual cells are bent back under the sides of the tapetum cup and consequently lie between it and the eye-capsule. This form of a tapetum has been figured by Widman, whose figures I copy. Figure 169 1, repre- sents a section of a prebacillar eye of Amaurobius cut at right angles to the longer axis of the tapetum; and (Fig. 169, 2,) repre- sents a section lengthwise of the tapetum slit. These two figures show a peculiar condition of the corneal hypodermis which exists in some eyes of spiders. The nuclear ends of the cells are crowded to one side; the result is that in one section these cells are cut lengthwise; in the other, transversely. The third type of tapetum is in the form of a shallow cup whose sides are divided into many parallel strips by a series of cross slits running out each way at right angles to the long slit at the bottom of the cup; this type is termed the grate-form type. 164 The Internal Anatomy of Spiders pg.sl.~- The nerve fibres enter the retina through the cross slits as well as through the long one. Figure 170 is a diagram representing one end of a grate-form tapetum, the figure is a composite one, the upper half representing the tapetum, as observed by Shafer, of Lycosa helluo, and the lower half, that of Pardosa lapidicina. In this figure, /. si. represents the longitudinal slit and c. si., the cross slits; both of these are filled with pigment excepting the spaces occupied by the nerve fibres, sections of which are represented as white spots. The white spaces, t., alternating with the cross slits, represent the tapetum strips. Extending in from the rim of the cup, which is heavily pigmented, there is a strip of pigment, pg. 3/., upon each tapetum strip. In each half of the figure, the rod end, r., of several visual cells is repre- sented. These cells are sur- rounded by pigment except where they rest upon the tapetum. The pigment cells. — Cells con- taining a dark pigment occur in various situations in and about the eyes of spiders. These pig- ment cells, limiting as they do the transparent tracts that may be followed by the light, doubtless play an important part in the operation of the eye. A ring of hypodermal cells about the rim of the eye and immediately under the edge of the lens that contains pigment is termed the iris (Fig. 169, i). The iris pigment occurs both in the undifferentiated hypodermis and in the marginal cells of the corneal hypodermis. In eyes of the postbacillar type (the anterior median eyes) there are interstitial pigment cells between the visual cells (Fig. 167,). In some species the pigment cells extend to the corneal hypodermis; in others they reach only the proximal end of the optic rods. In eyes of the prebacillar tvpe (all eyes except the anterior [65 Fig. 170. DIAGRAM OF 0\TE END OF A GRATE-FORM TAPETUM (after Shafer) The Internal Anatomy of Spiders median) differing conditions occur in different species. In eyes with a funnel-form tapetum there is no pigment in front of the tapetum; but in the second type of funnel-form tapetum-eyes described above, there may be interstitial pigment-cells between the nuclear ends of those visual cells that bend around behind the tapetum. And in both the first and the second types of funnel-form tapetum-eyes there are pigment cells between the nerve fibres behind the tapetum. In the grate-form tapetum-eyes, not only are there pigment cells between the nerve fibres behind the tapetum, but they extend above the tapetum as well, surrounding the optic rods. In the prebacillar eyes of many spiders there is found a pigmented layer similar to the funnel-form tapetum in form and position and, doubtless, homologous with it. This layer has been termed, unhappily, a "pigmented tapetum." But as it can- not reflect light, owing to its being pigmented, it cannot properly be called a tapetum. Finally, in some cases, a prebacillar eye is divided by a thick sheet of pigment into two portions, a larger median and a smaller lateral. In these divided eyes the visual cells differ in form in the two parts of the retina; and the form of the tapetum may differ in the two parts. Nocturnal eyes and diurnal eyes. — In the case of many spiders that live in the dark or that frequent shady places some of the eyes are pearly white. It is believed that such eyes are fitted for seeing in a faint light; they have been termed, therefore, nocturnal eyes. On the other hand, those eyes that are dark in colour are termed diurnal eyes. Considerable use is made of this distinction in the classification of spiders. It is of interest, therefore, to determine whether the pearly white eyes are fitted for nocturnal vision or not; and if so, to determine in what respect they differ from the so-called diurnal eyes.* Strictly speaking, any eye furnished with a tapetum, that is with a reflecting structure so placed behind the retina that the light entering the eye is made to traverse the retina a second time, must be considered a nocturnal eye. It does not follow, however, that every eye provided with a •At my suggestion, the working out of this problem was undertaken by Mr. George D. Shafer in the entomological laboratory of Cornell University. The morphological data given below as well as some of that given above are drawn from a thesis by Mr. Shafer, which, at the present writing, is unpublished. 1 66 The Internal Anatomy of Spiders tapetum can be recognized as a nocturnal eye by its colour when viewed externally. In order that the eye may give forth the pearly lustre it must be comparatively free from pigment between the tapetum and the cornea; for if this is not the case, the re- flected light will be absorbed to such an extent that the eye will not glisten. As no postbacillar eyes (anterior median) have been found in which there is a tapetum, it is probable that these eyes are never nocturnal. It should be noted, however, that in a few cases, as in Meta for example, the anterior median eyes have the pearly white lustre. A careful study of these eyes shows that there is no tapetum present, the retina immediately behind the optic rods being densely packed with interstitial pigment cells. The pearly lustre is due, therefore, to some other cause than the presence of a tapetum, and these eyes are only apparently noc- turnal. The pearly white prebacillar eyes of several genera (Pholcus, Theridion, Agelena, Clubiona, Tracbelas, Meta, and Amaurobius) were studied by Mr. Shafer. It was found that in each there is a funnel-form tapetum, and that there is no pigment between the tapetum and the cornea. These eyes are, therefore, truly noc- turnal; and the pearly lustre is doubtless due to the presence of the tapetum. In the prebacillar eyes of Pardosa, Lycosa, and Misumena, for example, a grate-form tapetum was found. These eyes are, therefore, strictly speaking, nocturnal. But as in the grate-form tapetum-eyes the pigment cells extend in front of the retina, surrounding the optic rods, but little light can be reflected out of the eye. On this account these eyes are apparently diurnal. To sum up the results it can be said that certain diurnal eyes (the anterior median eyes of Meta, for example) are appar- rently nocturnal; and that many nocturnal eyes (those having a grate-form tapetum) are apparently diurnal. In other words the presence or absence of a pearl}- lustre is not sufficient to determine whether an eye is nocturnal or diurnal. The eye-muscle. — Fach anterior median eye is provided with a muscle extending from the body-wall to the eye-capsule. No eye-muscles have been observed connected with any of the pre- bacillar eyes in true spiders. 167 The Internal Anatomy of Spiders d. THE LYRIFORM ORGANS There are found in several of the orders of the Arachnida organs of a peculiar type, the function of which has not been determined, but which have been supposed to be organs of hearing. They occur in spiders, in the Phalangida, the Pedipalpida, and in the Pseudoscorpionida, and are known as the lyriform organs, These organs vary greatly in form but agree in their essential features. The distinctly characteristic external feature is a slit in the cuticula in which there is a wider, oval, central portion, and, on each side of this, a long, narrow portion, which may or may not taper to a point. At the bottom of this slit there is a thin layer of the cuticula, so that the slit does not reach the body- , _ V*** cavity. These slits occur in the sternum and in the cuticula of most y~* of the segments of the legs, except fhVr: the tarsi, and of the mouth-parts. aJUiIjW They are extremely small; but are very constant in their form and in their position. In the sternum the slits may occur singly or in groups. But the more characteristic form of these organs, and the one that suggested the name lyriform, is found on the appendages, where they usually occur near the distal end of a segment; but Fig. 171. lyriform organs sometimes they are found near the middle of a segment. In this type there are several slits grouped side by side; and the cuticula sur- rounding the group of slits, as well as that of the spaces between them is greatly thickened (Fig. 171). The spaces between the slits suggest the cords, and the outer rim of the organ, the frame of a lyre, hence the name lyriform. In Fig. 171, a represents the lyriform organ in the metatarsus of the fourth leg of Argy- rodcs irigonus; and b that found in the same position in Theridion frondeum. As to the internal structure of the lyriform organs, it has been found that there is beneath each slit a nerve-end-cell. This 168 The Internal Anatomy of Spiders cell is elongate, with a nucleus at its proximal end, near its con- nection with a nerve, and with the distal end long and slender, and extending to the thin layer of cuticula limiting the slit within. According to Bertkau ('78), who discovered these organs, the nerve-end-cell terminates in a small chitinous rod which rests against the thin layer of cuticula; but this rod is not described by later writers, and is not now believed to exist. The observations of Bertkau led to the belief that the lyri- form organs are auditory in function. But the failure of other observers to discover scolopalae or auditory pins in the nerve- end-cells connected with them has made this conclusion doubtful. A detailed description of the lyriform organs has been pub- lished by Mr. N. E. Mclndoo since the preceding account was put in type. (Proc. Acad. Nat. Sci. Phil. 191 1, pp. 375—418). The results of Mr. Mclndoo's experiments indicate that the lyriform organs are olfactory in function. e. THE ORGANS OF TOUCH The organs of touch of spiders are distributed generally over the surface of the body. They are hollow hairs or setae each furnished with a nerve. The structure of such hairs has been described on page 140, and is illustrated by Fig. 146. It is probable that the nerves of the hairs are connected with a subhypodermal nerve-plexus as is well-known to be the case with insects. Traces of such a nerve-plexus have been observed by Bernard ('96) in the Solpugida. /. THE ORGANS OF TASTE AND OF SMELL Very little has been written regarding the organs of taste and of smell of spiders; and it is still a question whether organs of either of these senses exist among spiders or are wanting. It may be, as indicated above, that the lyriform organs are olfactory. THE GLANDS OF SPIDERS With the exception of the poison glands and the silk glands, the glands of spiders have received comparatively little attention. The moulting of spiders has been described in great detail by Wagner ('88); and reference is made by him to the moulting fluid 169 The Internal Anatomy of Spiders which facilitates the shedding of the old cuticula; but I find no reference to the moulting fluid glands. Doubtless there are in spiders, as there are in insects, modified hypodermal cells that produce the moulting fluid. Several glands have been described connected with the diges- tive organs that may function as salivary glands. These occur in the endites and in the rostrum. But the most prominent of the glands connected with the mouth-parts are those that open through the chelicerae and produce the venom. Glands which open in the coxal segment of the third pair of legs in tarantulas and in some true spiders have been observed; these are termed coxal glands. a. THE POISON GLANDS The poison-glands are two in number and are situated in the true spiders in the anterior part of the cephalothorax (Fig. 143). Each gland discharges its product through a long slender duct which opens near the tip of the claw of the chelicera of the cor- responding side of the body. In the tarantulas each poison gland is situated in the basal segment of a chelicera. The glands are sac-like in form; the lumen of the sac serves as a reservoir of venom; the wall is composed of excreting cells, supported by a layer of connective tissue, and there is a layer of muscle fibres surrounding the sac. The fibres of the muscle layer are arranged in a spiral manner. b. THE SILK-GLANDS The term silk is ordinarily used to designate the thread spun by the silkworm, Bombyx mori, from which nearly all of our silken fabrics are made; but by entomologists the term is also applied to other similar products. In this sense, silk is produced by various animals and is used by them for many different pur- poses, Among insects there is considerable variation in the structure and position of the silk organs; thus while with caterpillars the silk is produced by modified salivary glands, and is spun from a spinneret situated near the mouth; with ant-lions it is produced by modified Malpighian tubes and is spun from the caudal end of the alimentary canal. It is obvious, therefore, that silk-pro- 170 The Internal Anatomy of Spiders ducing organs have arisen independently in different races of animals. The silk organs of spiders are the most complicated silk organs known. This condition might be expected from the fact that a single species of spider spins several distinct kinds of silk; thus, for example, an orb-weaving spider spins five different kinds of silk. A detailed account of the different kinds of silk spun by spiders is given in the following chapter; and in the preceding chapter the external spinning organs are described. In this we have to consider the internal silk organs, the glands that produce the silk. As spiders spin several kinds of silk it is obvious that there are several kinds of silk glands differing in function. Seven different kinds of silk glands have been recognized. These differ in form, in number, in colour, in the structure of their ducts, and in the nature of their products. No spider has been found to possess all of the seven kinds of silk glands; but three of the kinds have been found in all species studied from this point of view; and a fourth is wanting in only two families. The three other kinds are each characteristic of a particular group of spiders, and no two of them are found to- gether. Each of the three groups of spiders that possesses a characteristic kind possesses also the first four kinds. Hence the presence of five kinds in a single spider is common. Much has been written on this subject; but the paper that has been of the most service in the preparation of this account is one by Apstein ('89). I have followed Apstein quite closely in my account of the structure of the glands; but in several cases my own observations do not confirm his conclusions regarding their function. The different kinds of silk are spun from different types of spinning tubes (Fig. 172), which are described on page 135. The aciniform or berry-shaped glands. — There are four clusters of these glands, one for each of the hind and middle spinnerets SPINNING TUBES 171 The Internal Anatomy of Spiders (Fig. 143). They have been found in all species studied. In Aranea there are about one hundred in each cluster or four hundred in all; but in some spiders there are only a few of them. They open through the first type of spinning tube, those with a long, more or less curved base, and a slender straight tip (Fig. 172, a). The name applied to these glands was suggested by the botanical term acinus, which is applied to one of the kernels of a fruit like a raspberry. A single gland resembles an acinus in form; each of the four clusters of these glands resembles a berry. The aciniform glands are nearly spherical and consist of an epithelium invested by a peritoneal membrane (Fig. 173). The epithelium is not continued into the duct. All parts of the gland give the same reaction to stains. I have determined by direct observation that the swathing band is formed of silk from these glands. This fact is easily determined by feeding a spider confined in a glass tube. Thepyriformor pear-shaped glands. — There are two clusters of these glands, one for each of the fore spinnerets (Fig. 143). They have been found in all species studied. In Aranea there are Fig. '173. about one hundred in each cluster, or Fig. 174. an two hundred in all, but some spiders A ACINIFORM . , , , ., T, PYRIFORM gland nave ornv a 'ew °' them. 1 hey open gland through spinning tubes of the second type (Fig. 172, b), in which the basal part is short, the tip twice as long as the base and curved. These glands are elongate and consist of an epithelium in- vested by a peritoneal membrane (Fig. 174). The epithelium is not continued into the duct. The part of the gland next its mouth gives a darker colour reaction to stains. Owing to this these glands are easily distinguished in stained preparations. The function of the pyriform glands is the formation of the attachment disks. The making of these disks by a spider con- fined in a vial can be easily observed. The ampullate or bellied glands. — These are referred to by certain writers as the cylindrical glands; but this name has been applied to the type of glands described next. There are usually four ampullate glands; but frequently there are six or eight, and 172 The Internal Anatomy of Spiders in some spiders there are as many as twelve. They are large, long glands, more or less cylindrical in outline (Fig. 143, and Fig. 175). The glands consist of an epithelium invested by a peri- toneal membrane. The epithelium is continued into the duct, which also has a chitinous intima. Each gland opens through a spigot (Fig. 172 c). In the usual condi- tion, when there are four of these glands, the spigots are located one on the inner side of each of the fore and middle spinnerets. The ampullate glands occur in all species examined. They are termed am- pullate because each is furnished with an ampulla or sac-like dilation. The drag-line and the dry threads of webs are made of silk from the ampullate glands. The fact that the drag-line is composed of only two or four strands and that it comes from these glands was dis- covered by Warburton ('90). The source of the elastic element of the viscid thread of the orb-weaving spiders has not been determined. It appears to come from the centre of the group of spinnerets; as it consists of two strands of considerable size, it is evidently spun from two spigots. As the drag-line of orb-weavers usually consists of two strands, I infer that in these spiders two of the ampullate glands have been so modified that they produce elastic silk. Wilder ('66) demon- strated that the yellow silk of Nephila, which is the Fig I7S- viscid silk, is spun from the fore spinnerets. an / he cylindrical glands. — I hese glands are com- gland monly present in female spiders; but are wanting in the Dysderidae and in the Attidae. There are usually six of them; but sometimes there are many. In males there is a smaller, number or they are wanting. In the usual case, where there are six cylindrical glands, one opens on the outside of each middle spinneret, and two open on the inside of each hind spinneret. Each opens by a spigot similar to the spigots of the ampullate glands, but with a wider opening (Fig. 172, d). 173 The Internal Anatomy of Spiders These glands He directly on the ventral side of the body cavity; they are long, cylindrical, of uniform diameter, and convoluted (Fig. 176). They resemble in structure the ampullate glands. The function of these glands is the production of the silk of which the egg-sac is made. Spiders of the two families in which they are wanting do not spin true egg-sacs. This is the only case of a sexual difference in the silk glands of spiders. The aggregate or treeform glands. — These are found only in the orb-weaving spiders and in the Linyphiidae and Theridiidae. They are a symmetrical in form, being irregularly branched and lobed. (Fig. 177.) The duct bears on its middle part many knobs which are filled with cells. There are six of these glands, four large and two small. Three open near together on the inner surface of each hind spinneret, through spigots the tip of which is pointed (Fig. 1 72 e). The term aggregate was suggested by the lobed form of the glands, which gives them a compound appearance. It is believed that the function of these glands is to secrete the viscid drops of the viscid and elastic thread. As these glands are found in the Theridiidae, as well as in the orb-weavers, it is important to determine whether viscid threads occur in the webs of these spiders. It is certain that they are uncommon or at least are inconspicuous, but they have been observed in the webs of Linyphia, Steatoda, and Theridion. The lobed glands. — These occur only in the Theridiidae and are either two or four in number. They open on the hind spinnerets through spigots without a tip (Fig. 178). The lobed glands are very irregular in form, consisting of a mass of irregular lobes (Fig. 179). The silk of which the swathing film of the Theridiidae is made is secreted by the lobed glands. Correlated with their presence is the development of only a small number of aciniform glands. The cribellum glands. — These are found only in those fami- lies in which a cribellum and calamistrum are present. They open on the cribellum through exceedingly small pores (Fig. 141, p. 135). The glands are exceedingly numerous; they are spherical and are often grouped; that is several many be enclosed in a common sheath of peritoneal membrane. It is probable that the function of the cribellum glands is to secrete the woof of the hackled band. Figure 180 represents the relative position of the silk glands in a spider. 174 Fig. 176. A CYLINDRICAL GLAND Fig. 1 r<>. A LOBED GLAND Fig. 177. AN AGGREGATE GLAND Fig. 178. HIM) SPINN1 II 1 01 - II \Kih\., SHOWING run SPINNERETS W [THOUT A TIP (after Apsl in -I 1 1 [ON OF VBDOMEN SHOW 1 ■'■ il.K GLAJ (after Ap '73 The Internal Anatomy of Spiders W K W Q hH co o CO W m D H O 2 »-• 2 CO w H Q 2 < CO Q 2 < O -J CO « EC 1/5 _2 ».a *^ 41 1/5 r2 'u 1/5 O C p££ 1/5 o > J S c Z o p u z 3 00 IS -5 c 05 E igline an read of s also i C/5 1 6C 0) §1 oo c IE 4) "O o t: U. CTJ CO u < he drs dry th perhap silk XI o co 0. i« h- cu 45 0) ■ ■ JC J= >, J» ^^ 4-< c -e 1/5 1/5 0/ 1/5 05 Wanting in Attidas and Dysderidae 3H N w ui j S < 4> 22 O.T3 ™ 2 — 1/5 < 45 Ji i/> 3 — on < CU ■ — CUT) — V) < Argiopidae, 1 phiidae and ridiidae 41 H J2 "a/ X "C u Ul 1/1 w 03 D H O Z z z El M f- LL O UI a. >■ H 4-» 1/5 *- T3 C O o 0/ co 4-1 o op 'S. co 4-J o op '5. co Spigot with pointed tip Spigot with- out tip "j5 E 1/5 U 41 > t/5 1/5 ^ 0) <u 41 i/) 41 £ T3 2 _C ul H — — 4) '55 *V5 Ih I 1- Q c 41 C 45 - c.S- Z E o o o c c o c c o m O i/5 1/5 ^ 0) 41 -*— 45 £ 32 ."2 CO — 41 I- <*- *l/5 1_ *V5 -J Q Q <u Ol c o c c 3 O c % o o o o +_ sx> c Im a. co a 41 O O i- c .5 3 o i/l .4) o U- o 1/5 <*- 8.22 ri c « U.S 4> UJ * 1/5 U 4) * 1/5 0) aj — B^ O • - 6C OO i- — Tf C c3 1/5 Q Z < CQ s a Z 1/1 u 1/5 u 3 CO 3 o 6 in female times ma or want male "^ 1/5 Ih O E Ih 41 > O Ul X H rfO ^D Ul S < E * l- -C O 1/5 «*- t o"2 E n c ° C OD'B 00 05 41 t_ T3 41 X O E _3 X3 z c b Oh — E m ">5 U J *c <X> < o oo" < U a a 'a be a o n C> 11) 3 05 > U3 S 5 a g 05 Ol -a jj H H I76 CHAPTER IV: THE LIFE OF SPIDERS The careful observer of the ways of spiders soon learns that the members of the different families differ greatly in their modes of life; and that even within the limits of a single family striking variations exist. In fact each species, while agreeing with closely allied forms in the more general features of its life history, ex- hibits specific pecularities. There is given in later pages of this book, so far as the limits •of space will permit, what is known regarding the characteristic habits of each of the families of North American spiders, and of some of the more common species in each. But in order to avoid repetition those features that are common to all or to many species are discussed here. i. — METHODS OF STUDY The study of the life of spiders is essentially a field study a few species live in our dwellings, and some others can be kept in confinement, but the great majority of them can be best observed in the open air; and so abundant are these creatures that one need never lack materials for study during the warmer parts of the year. Spiders live in a great variety of situations. A few species seem to prefer the angles of buildings; many are usuallv found among shrubbery; some stretch their webs high in trees- others build among the low herbage of meadows and pastures; the mem- bers of several families run over the surface of the ground or lurk beneath stones; and certain kinds dig burrows in the earth The student should therefore pursue his studies in as great a variety of situations as possible. A collecting outfit.— For the collection and preservation of spiders only a small equipment of apparatus is necessarv A collecting outfit should include bottles of alcohol for the preserva- tion of specimens, empty bottles for bringing home specimens alive, a pocket lens, a piece of black cloth, preferably velvet, to •77 The Life of Spiders place behind webs when studying them, and, most important of all, material for taking notes. Methods of collecting. — The most instructive method of collecting spiders is by carefully seeking for them and observing their habits before taking specimens; this is especially true of the web-building species. Many other species are to be found by overturning stones and other objects lying on the ground and by tearing off the bark from dead trees, logs, and stumps. But if it is desired to make as complete a collection as pos- sible of the species of a locality, other methods must also be used. Of these those known as sweeping and as sifting are the more important. In sweeping, an insect net is used and the foliage of shrubs and trees is beaten, and herbage is swept, as in the well-known method of collecting insects. In sifting, dead leaves are collected from the ground and shaken in a large sieve over a sheet of paper. The apparatus devised by Professor Berlese of Florence, and described by Dr. L. O. Howard in Entomological News for February, 1906, is very useful for collecting the small spiders that live among dead leaves and other rubbish. This apparatus consists of a metal cylinder in which the rubbish is placed and to which heat is applied causing the spiders and other animals in it to move down into a receptacle placed to catch them The preservation of specimens. — Owing to the softness of the body, spiders cannot be well preserved dry. The preserva- tive fluid that is usually employed is alcohol; it should not be diluted, but used of the full strength of commercial alcohol. Care should be taken not to put too many specimens in a bottle, and if the specimens are large the alcohol should be changed after one or two days, as the alcohol first used will be diluted by the fluid of the body. If specimens are to be preserved permanently, the bottles should be provided with rubber stoppers, as the alcohol is liable to evaporate from bottles closed with cork. In some of the larger collections the specimens are put in small corked bottles and these bottles are stored in larger bottles or fruit jars filled with alcohol and tightly closed. The egg-sacs and many kinds of nests of spiders can be mounted and preserved dry; but in most cases it is impracticable 178 The Life of Spiders to preserve specimens of the webs; here photographs must take the place of the actual specimens. 1 1 is possible, however, to make beautiful mounts of the central and more characteristic portion of orb-webs. This is done by mounting the web between two plates of glass. Take two pieces of glass of the same size; prepare one of these by fastening a narrow strip of adhesive paper along the edges of one face; then carefully press the other piece of glass against the web to be pre- served; the viscid silk will cause the web to adhere to the glass, and if the operation be carefully performed the relation of the different lines will be preserved; the lines that extend beyond the edge of the glass should then be wiped away, using care not to disturb the position of the lines upon the glass; then cover the web with the other piece of glass which will be held a short distance away from the web by the strip of paper on its edge; the two pieces of glass are then fastened together by pasting a strip of gummed paper over the edges of them. The kind used in mounting lantern slides is the most available form of adhesive paper for this purpose. The laboratory equipment — -The laboratory should be furnished with a dissecting microscope, which is the most con- venient type of microscope for use in the study of the classi- fication of spiders, and with a compound microscope. 1 use also, with great satisfaction, the Pfeiffer dissecting microscope which gives an erect image and which is made to fit upon the stand of an ordinary dissecting microscope. For anatomical work the stereoscopic microscope, made by Zeiss, is very useful. There is also needed a supply of watch glasses, forceps, dissecting needles, a measuring rule, and a glass tube fitted with a rubber bulb, like a pen filler, tor picking up and transferring minute specimens in alcohol. Some method of storing the specimens in systematic order, so that allied forms shall be kept together and so that any desired specimen can be easily found, should be adopted. 1 use bent neck vials, stoppered with rubber, mounted on blocks, and stored in systematic sequence in the same kind of drawers as we use for the storing of insects. In some collections the bottles are stored in drawers fitted with series of holes for the reception of the bottles; and in other collections the small bottles are stored in larger ones, as already described, and these are arranged on the shelves of a cabinet. 179 The Life of Spiders On photographing spiders. — It is exceedingly difficult to induce living spiders to pose for their photographs. Sometimes, in the case of large species, where it is not necessary to approach the camera too closely to the spider, a good photograph can be obtained of one in its natural attitude, and I have taken photo- graphs of running spiders by enclosing them in a plate glass box and photographing through one side of the box. As a rule, how- ever, it is necessary to kill a spider before a satisfactory photo- graph can be made of it. The specimen should be killed in a cyanide bottle, and then either posed dry on a piece of cardboard or placed in a porcelain dish of alcohol and photographed with a vertical camera. This must be done promptly while the legs and palpi are flexible and before they become curled up. Sometimes, in the case of brightly marked species, better results are obtained if a colour screen is used. On photographing spider wehs. — If one wishes to take photo- graphs of spider webs, special preparations should be made for it. Photographs of webs taken in the field are seldom satis- factory. Only rarely can a web be found in a suitable position as regards lighting and background, and in a satisfactory state of preservation. When possible, the spider whose web it is desired to photo- graph, should be induced to build a web where it cannot be in- jured by wind or insects and where the nature of the lighting and of the background can be controlled. Many of the pictures in this volume are from photographs of "made to order" webs. These webs were made in the glass house of our insectary, which resembles an ordinary greenhouse. Any room suitable for photographic work would serve for this purpose. The most easily obtained webs were those of spiders that build upon shrubs or trees. Having found such a web in the field, the branch upon which it was built was carefully cut and carried, with the spider and web upon it, into the insectary and firmly fixed into the earth in a large flower pot. This permitted the moving of the branch without disturbing the web, when it was desired to pose it for a photograph. If the spider was not unduly disturbed it remained on its web in the new situation, and in most cases repaired the web during the first or second night following. Usually the outer framework 1 80 The Life of Spiders was left but the central and more characteristic portions of the web were entirely rebuilt. This new web being protected from wind and from insects often remained in a perfect condition for a considerable time, giving ample opportunity for the study and the photographing of it. Owing to the extreme delicacy of the threads of which a web is made very careful lighting of it is necessary. By simply moving the flower pot containing the branch, the web can be put in the most favourable position. As to the background, good results were obtained by hanging a piece of black velvet behind the web; this substance reflects very little light and makes a good contrast with the light lines of the web. But the most perfect results were obtained by the use O-o^O— °— o Fig. 181. VISCID SILK OF ARANEA of a dark hole for a background. This was obtained by using an open box about five feet deep, three feet wide, and three feet long. This was lined with black velvet and placed upon its side. The web to be photographed was then placed before the opening of the box. The bottom of the box, which served as the back- ground, being in the shadow of the sides reflected almost no light. Frequently the getting of a photograph of a web was not so simple as in the case of those built on shrubs and trees; sonic of the special devices used for this purpose are described in the accounts of the webs given later. On photographing threads, of silk. — After making many unsuccessful attempts to make photomicrographs of silk, I devised a very simple method. Two small pins are inserted in l8l The Life of Spiders the end of a narrow strip of cork; these pins are about one third inch apart; by pressing these pins against a thread which it is desired to photograph a section of the thread is obtained stretched between the pins; thus mounted, the thread can be kept from injury by contact with any object; the piece of cork bearing the pins and silk is placed on the stage of a microscope so that the silk is in front of the objective. It is now easy to study the silk; and by combining the microscope with a camera in the ordinary way, to make a photomicrograph of it. Figure 181 was made from a photograph obtained in this way. II.— THE DEVELOPMENT OF SPIDERS The egg-sac— The eggs of spiders are laid in a mass and are usually protected to a greater or less extent by a covering of silk, the egg-sac or cocoon; but sometimes they are merely agglutinated and are without a silken covering; this is the case in some of the Pholcidae. Sometimes the egg-sac is so thin that it does not conceal the eggs, being merely a loose web of threads; in other cases it is very elaborate in structure. Several types of egg-sacs are discussed later in the discussion of the motherhood of spiders. The life within the egg-sac. — As a rule the eggs hatch in a comparatively short time after they are laid. The egg-shell is broken, in the case of certain spiders at least, by a tooth on the base of the pedipalps. Although the eggs hatch soon after they are laid, the spiderlings may remain within the egg-sac for a long time. Very many of the spiders living in the North pass the long winter as spiderlings within the egg-sac. With these the eggs are laid in the autumn, the spiderlings soon hatch, but remain in the egg-sac till the following spring. Thus it may happen that a spider whose entire life is one year in duration spends nearly or quite one half of this period within the egg-sac. On the other hand, the young of many species leave the egg-sac soon after hatching. According to the observations of Dr. B. G. Wilder ('73a) some of the young of Miranda aurantia feed upon their weaker brothers and sisters; so that from an egg-sac that in early winter contains a large number of spiderlings there emerge in the spring a much smaller number of partly grown spiders. How general 182 The Life of Spiders this habit of cannibalism is has not been determined. McCook states that the young of the orb-weavers prey upon each other after they leave the egg-sac. The moulting of the cuticula. — Spiders, like insects, shed, from time to time, an outer layer of the cuticula of the body. This process is termed moulting and the cast skin is called the exuviae. The number of the moults and the intervals between them varies with different species, and has been determined in only a few cases. Blackwall states that Epeira catophylla moults five times and Tegenaria civtlis, nine times. Wagner found that the young of Trochosa singoriensis moulted four times before beginning to lead .in independent life. The cuticula of the cephalothorax and of its appendages, the legs and mouth-parts, is firm and inelastic, being hardened by a horny sub- stance known as chitin. Ow- ing to this it will not stretch enough to allow for the growth of the spider. The result is, that from time to time, the . . . ,. Fig. 182. TARSUS OF A MOULTING SPIDER cuticula becomes too small dolomedes scrtpti for the spider and must be shed. But before this is done a new cuticula is formed beneath the old one; then the old skin bursts open, and the spider casting it off is clothed in a soft skin, which stretches to accom- modate the increased size of the body. Very soon, however, this new skin becomes hardened with chitin, and after a time it in turn must be shed. Before the old cuticula is shed it is loosened by a fluid, the moulting fluid, which is excreted from glands that open through the new cuticula. Figure 182 represents the tarsus of a moulting spider; here the old skin can be seen separated from the new ; this is especially clear in the region of the claws, there being apparently two pairs of claws; but the outer pair is merely the loosened cuticula of the claws. After the old cuticula is loosened, it splits along the sides of the body and in front of the eyes; the slit being just above the base of the legs and mouth-parts and extending back on each side upon the abdomen. I hat portion of the old cuticula that 183 The Life of Spiders had covered the dorsal aspect of the cephalothorax is lifted off like a lid and remains attached to the abdominal portion (Fig. 182 bis). Through the opening thus made the body is worked out, and the appendages one after the other are pulled from their old coverings. In addition to the mechanical reason for the moult, the allow- ing of the increase in size of the body, there are doubtless physi- ological reasons for it also. In spiders the old cuticula of the abdomen is about as elastic as the new one, still the moult includes this part of the body as well as the fir- mer portions. At each moult the spider is clothed with a complete coat of new hairs. When the function of the hairs as sense organs is considered, it is seen that their renewal at intervals is very important. Other physiological reasons for the moult have been suggested, but as yet they are not well understood. Transformations. — In the course of their development, spiders undergo comparatively slight changes in form. Their development is comparable to that of those insects that undergo an incomplete metamorphosis. They increase in size, and the proportions of the different parts of the body undergo a greater or less change; but there is no marked change in form as there is with those insects that undergo a complete metamorphosis. The most marked change takes place at the last .moult, when the development of the sexual organs is completed. Previous to this moult, the tarsus of the pedipalp of the male is merely a club-like segment in appearance; but when the cuticula is shed for the last time, the exceedingly complicated organ already described is disclosed. So also in the case of the female of those Fig. 182 bis. MOULTED SKIN OF A SPIDER, DOLOMEDES URINATOR, MALE 184 The Life of Spiders species that have an epigynum, this organ is not exposed till the last moult takes place. At this time too, the abdomen of the female may undergo a marked change in form, due to the growth of the eggs within it. The males of the hackled-thread weavers lose the cribellum and calamistrum at the last moult or have these organs greatly reduced. The reproduction of lost organs. — The reproducing of legs that have been lost by immature spiders is frequently observed. If a leg be lost by a young spider the wound soon heals, and at the succeeding moult the bud of a new leg appears. This bud increases in size at each succeeding moult; and in time, if the process begins early enough in the life of the spider, a functional leg is obtained. Figure 183 repre- sents a spider in which two legs, the left fore leg and the right hind leg, were being reproduced; this is a mechanical reproduction of a photograph of a spider in our collection. Fig. 183. A SPIDER REPRODUCING LOST LEGS III.— THE FOOD OF SPIDERS All spiders are carnivorous. Their prey consists chiefly of insects; but they will feed on other spiders that they can overcome, even on weaker members of their own species. This cannibalism is not confined to that of young spiders described in the preceding section, but is also true of adults. It is a common occurrence for the female to destroy the male of its own species, which is smaller and weaker. Besides insects and spiders other small animals are occasion- ally destroyed by these voracious creatures. The most striking instance of this is the destruction of small birds by a large South American tarantula, the bird-spider {Avicularia avicularia). 185 The Life of Spiders The habits of this spider were first described by Madam Merian (1647—1 717)- Most writers have doubted the truth of her statement; but it has been confirmed by Bates ("A Naturalist on the Amazon," p. 80). Although Simon is among those that doubt Madam Merian's account, he states that the Avicularia that he caught in Venezuela ran on the trunks of trees with as- tonishing rapidity (Simon '92, p. 170). And as the so-called bird- spider is very large, the body measuring two inches in length and the legs expanding seven inches, it is certainly large enough and strong enough to overcome some of the smaller birds. In fact several apparently well-authenticated instances of the de- struction of small vertebrate animals, including birds, a mouse, a fish, and a snake, by spiders that were much smaller than the Avicularia are given by McCook ('89. I. 235). But of course all such occurrences are very exceptional. The mouth of a spider is fitted only for the taking of liquid food. This it presses from its victim by means of its chelicerae and the endites of its pedipalps. Observations on spiders in confinement indicate that some of them at least require water frequently; but it is evident that others obtain moisture only by sucking the liquids of their victim. Although spiders are extremely voracious, they are capable of enduring long fasts. Blackwall states that a female Tberidion quadripunctatus was known to exist for eighteen months without nutriment in a vial closely corked. IV.— MEANS BY WHICH SPIDERS OBTAIN THEIR PREY Great differences exist among spiders as regards the ways in which they obtain their prey; some, the wandering spiders, stalk their prey; others lie in ambush for it; many trap it by means of snares; and a few live as commensals. The wandering spiders. — Among the more familiar examples of wandering spiders are the wolf-spiders (Lycosidse), the jumping spiders (Attidae), and most of the crab-spiders, (Thomisidaj). These run about in search of their prey and pounce upon it when an opportunity offers. The ambushing spiders, — Certain of the crab-spiders, as some species of the genus Misumena, hide in flowers and capture 186 The Life of Spiders insects that visit them, resembling in this respect the ambush-bugs; and many of the mining spiders lie in ambush at the entrance of their burrows, ar.d spring forth to seize insects that come near. The net-building spiders. — The great majority of sedentary spiders, as those that do not wander in search of prey are termed, spin webs or snares for the trapping of insects, and wait either upon or near the webs where they can easily rush upon an en- tangled insect. The commensal spiders. — Excellent examples of feeding at the same table with other species, or commensalism as it is termed, is exhibited by species of the genus Argyrodes. These small spiders live in the snares of larger web-building species and feed upon the smaller entrapped insects that are neglected by the owner of the web. Means of destroying the prey. — Spiders destroy their prey by means of venom secreted by a pair of glands in the cephalothorax; the ducts from these glands open, one on each side, through a minute pore near the tip of the claw of the chelicera. Most of the web-building species swathe their victims in a sheet of silk. The act of swathing can be easily observed by throwing a large insect into the web of a Miranda. 1 he spider first rushes at the insect and pierces it with the claws of its cheli- cerae, and then darts back into a position of safety; this may be repeated several times; or, if the spider is not afraid of its victim, the biting may be omitted. Then the spider approaches the insect and pulling out a sheet of silk from its spinnerets with one hind leg thrusts the sheet against the insect. In doing this the spider uses first one hind leg and then the other. In the case of a large Miranda this sheet of silk is sometimes an inch in length, the body of the spider being held that far from the insect; under these conditions the sheet can be seen to be composed of a very large number of parallel threads, probably a thread from each of the small spinning tubes of all the spinnerets enters into the composition of the sheet. As soon as the sheet is fastened to the insect the spider rolls the insect over and over and thus wraps it in its shroud. V.— THE SILK OF SPIDERS The silk glands have been described in the chapter on internal anatomy; and the spinning organs, in the one on external anatomy; 187 The Life of Spiders we have now to consider the nature and uses of the different kinds of silk. The dragline. — Most spiders as they move from place to place spin a thread, which marks their course; this thread has been termed the dragline. Draglines are the most commonly observed threads of spiders; it is by them that spiders drop from an elevated position to a lower one; it is of them that the irregular nets are largely composed; and the foundation of an orb-web is made of draglines. There is a commonly accepted error regarding the structure of a dragline. As the number of spinning tubes is large in the spiders most commonly studied, the orb-weavers, it has been inferred that in spinning a line the spider emits a delicate thread from each, and that all of these, some- times several hundred in number, blend into one. This is not the case; the dragline is composed of a small number, usually only two, compara- tively large threads. These, judging by their size are evidently spun from spigots. The attachment disks. — If a spider that is running along some object and Fig. 184. . . ii- • j_ i_ an attachment disk spinning a dragline as it goes be carefully observed, it will be seen to fasten this line at frequent intervals to the object on which it is. This is done by making what may be termed an attachment disk; such a disk is pictured by Fig. 184; it is composed of a large number of minute looped threads. The method of making an attachment disk can be easily observed by enclosing a living spider in a bottle, and watching it with a lens as it fastens its dragline to the sides of the bottle. This I have done many times; and in all of the cases that I have observed, the spider applied the fore spinnerets to the surface of the glass and by quickly spreading the organs apart and bring- ing them together again two or three times made the disk. An examination of the disk with a microscope shows that it is com- posed of a large number of fine threads. It is evident therefore that the silk of which it is made issues from the numerous small 188 The Life of Spiders spinning tubes of this pair of spinnerets and is therefore the prod- uct of the pyriform glands. The spiders that I have seen make attachment disks were Aranea frondosa and a species of Amau- robius. The following interesting observation was reported to me by Prof. Cyrus R. Crosby: — "The other day when attempting to capture an Aranea trifolia she attached her thread but had no time to change to the dragline and so spun a band of silk a foot long before she was able to make a new attachment and start the dragline." The swathing band. — The band of silk with which the orb- weaving spiders envelop their prey may be termed the swathing band. The method of making this band is described on an earlier page. I have watched the process many times, but owing to the timidity of the spiders observed, I have never been able to deter- mine to my complete satisfaction whether the silk comes from all of the spinnerets or only from the hind and middle ones. It is easily seen that the band is composed of a great number of fine threads and it appears to come from all of the spinnerets. If this is true, it is the product of both the pyriform and the acini- form glands. I have observed the making of the swathing band only by orb-weaving spiders; probably other spiders have similar habits. The swathing film. — Spiders of the family Theridiidae use in swathing their prey a film of silk which differs from the swathing band of the orb-weavers. This silk is emitted from two or four spigots, one or two as the case may be, on each of the hind spin- nerets. These spigots are the outlets of the lobed glands; which have been found only in this family. The viscid thread. — In the webs of orb-weaving spiders there occurs a peculiar viscid thread;