The Structure And Habits Of Spiders - free ebook by J. H. (James Henry) Emerton

THESTRUCTURE AND HABITSOFSPIDERS.

BY J. H. EMERTON . ILLUSTRATED. BOSTON: S. E. CASSINO &amp; CO., PUBLISHERS. 1883. COPYRIGHT. By S. E. CASSINO. 1878. Electrotyped By C. J. Peters &amp; Son, Boston....

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PREFACE.

The object of this book is to give a plain account of the best known habits of spiders, and as much of their anatomy and classification as is necessary to understand these habits. The portion on the spinning and flying habits is copied chiefly from Blackwall and Menge; that on the trap-door spiders from Moggridge; and the habits of Nephila and Hyptiotes, from Wilder. The observations of these authors have been repeated as far as possible, and some changes and additions made to their accounts of

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LEGS.

The legs are used chiefly for running, jumping, and climbing; but the front pair serve often as feelers, being held up before the body while the spider walks steadily enough on the other six. One or both of the hinder legs are used to guide the thread in spinning; the spider at the same time walking or climbing about with the other six or seven. The legs are seven-jointed; and on the terminal joint are three claws, Fig. 2 , A, B, C, and various hair and spines. In many spiders a brush of hairs t

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PALPI.

In front of the legs are the palpi, Fig. 1 , C, C,—a smaller pair of limbs, with six joints and only one claw or none. They are used as feelers, and for handling food, and, in the males, carry the curious palpal organs, which will be described farther on. The basal joints, Fig. 1 , E, of the palpi are flattened out, and serve as chewing-organs, called “maxillæ.” Fig. 3. Mr. Mason has lately described, in the Transactions of the Entomological Society of London, a large spider which has teeth on t

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MANDIBLES.

The front pair of limbs, the mandibles, Fig. 1 , D, are two-jointed. The basal joint is usually short and stout, and furnished on the inner side with teeth and hairs. The terminal joint is a small and sharp claw, which can be closed against the basal joint when not in use....

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ABDOMEN.

On the under side of the abdomen, just behind the last pair of legs, are two hard, smooth patches, which cover the front pair of breathing-organs, the openings to which are two little slits at Fig. 1 , H. Between these is the opening of the reproductive organs, and, in female spiders, the epigynum, Fig. 1 , J,—an apparatus for holding the reproductive cells of the male. At the end of the body are the spinnerets, which will be described in another chapter. There are three pairs of them; but many

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INTESTINE.

Fig. 5 is a section of the same spider. The mouth is at a b , just under and behind the mandibles, and between the maxillæ. It has an upper, a , and under lip, b , each lined with a horny plate, in the middle of which runs a groove. When the lips are closed, the two grooves form a tube, which leads to the œsophagus, c , and so into the stomach. At the end of the œsophagus is the sucking-stomach. This consists of a flattened tube, to the top of which is attached a muscle, d , connected with the g

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HEART.

Over the intestine, and parallel with it, is the heart, p , a muscular tube, with openings along the sides to receive the blood, and branches through which it flows to different parts of the body. The greater part of the blood enters at the front of the heart, and passes backward into the abdomen, or forward into the thorax....

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BREATHING-ORGANS.

In the front of the abdomen are the principal breathing-organs,—a pair of sacs, R, containing a number of thin plates, through which the blood passes on its way to the heart. Besides these, there is a pair of branching air-tubes, t , opening near the spinnerets....

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NERVOUS SYSTEM.

The nervous system has a large ganglion, J, in the thorax, from which branches, i , pass to the limbs and abdomen. At the front end two branches extend upward, each side of the œsophagus, to two smaller ganglia, k , from which pass nerves to the mandibles and eyes. The reproductive organs, S, lie along the under side of the abdomen, and open between the two air-sacs. The spinning-glands, u , lie above the spinnerets, and along the under side of the abdomen. They will be more fully described in t

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POISON-GLANDS.

The poison-glands, n , are partly in the basal joints of the mandibles, and partly in the head, and discharge by a tube which opens at the point of the claw of the mandible, Fig. 15 , a ....

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CLASSIFICATION.

There is not room in this book to explain the classification of spiders into genera and species; but a description of the following well-marked groups, which contain nine-tenths of all spiders, will give a general idea of the differences among them, and help to understand what follows. Fig. 6....

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MYGALIDÆ

This family includes the largest known spiders. The body is usually very hairy and dark-colored. Most species have only four spinnerets; and one pair of these are long, and are turned up behind the abdomen. They have four air-sacs under the front of the abdomen, instead of two, as other spiders. Their mandibles are very large, and work up and down, instead of sidewise. The eyes are collected together on the front of the head. They live only in warm countries. Specimens from South America are exh

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DYSDERIDÆ.

A small family of spiders with only six eyes. They have also four breathing-holes in the front of the abdomen; but one pair leads to branched tubes instead of sacs. They are usually found under stones, with their legs drawn up close to their bodies, but can move very quickly when so inclined. Very few species are known, and none are common, in North America. Fig. 7 is Dysdera interrita enlarged. Below are the eyes as seen from in front....

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DRASSIDÆ.

A large family of spiders, varying greatly in shape, color, and habits. Most of them are dull colored, and live under stones, or in silk tubes on plants, and make no webs for catching insects. Their eyes are small, and arranged in two rows on the front of the head. Their feet have two claws and a bunch of flat hairs. The spinnerets are usually long enough to extend a little behind the abdomen. Fig. 8 is a Drassus , and the eyes as seen from in front. Fig. 7. Fig. 8....

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AGALENIDÆ.

Long-legged, brown spiders, with two spinnerets longer than the others, and extending out behind the body. They make flat webs, with a funnel-shaped tube at one side, Fig. 24 , in which the spider waits. Fig. 9 is Agalena nævia , the common grass spider. Fig. 9....

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CINIFLONIDÆ.

A family resembling the last, but having peculiar spinning-organs, which will be described farther on, Fig. 35 ....

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LYCOSIDÆ.

The running spiders. Very active spiders, living in open places, and catching their prey without webs. Their legs are long, the hind pair being the longest. The head is high, and the arrangement of the eyes peculiar to the family, Fig. 10 . Fig. 10....

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ATTIDÆ.

The jumping spiders. The body is usually short, and the head square. The arrangement of the eyes is characteristic, Fig. 11 , a . The two large ones in the middle give these spiders a more animated look than those of other families. The legs are short, and the front pair often stouter than the others. They can walk easily backwards or sidewise, and jump a long distance. Fig. 11 is the common gray jumping spider enlarged. Fig. 11. Fig. 11 a ....

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THOMISIDÆ.

The crab spiders. The body is usually flat, and wide behind. The front two pair of legs are longer than the others, and so bent that the spider can use them when in a narrow crack. Some of them, like crabs, walk better sidewise than forwards. Like the running and jumping spiders, they make no webs for catching food. The eyes are small, and simply arranged in two rows, Fig. 12 . Fig. 12....

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THERIDIIDÆ.

The largest family of spiders. Most of them are small, with large rounded abdomens and slender legs. They live usually upside down, holding by their feet under their webs. They make large cobwebs of different shapes for different species, and depend for food on what is caught in them. To this group belongs the genus Erigone , containing a great number of the smallest spiders known. Fig. 13 is the common house Theridion enlarged. Fig. 13....

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EPEIRIDÆ.

The round-web spiders. Large spiders, with flat heads, and eyes wide apart, and short, round abdomens, Figs. 1 , 4 . They make webs formed of radiating lines crossed by other adhesive ones in a spiral or concentric loops, Fig. 28 . They hang in the web, head downward, or live upside down in a hole near by....

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CHAPTER II.EATING AND BITING.

The spiders are best known and hated as animals that bite. The biting apparatus is shown in Fig. 14 , which represents the head and mandibles of Epeira vulgaris , seen from in front. When not in use, the claw is closed up against the mandible between the rows of teeth; but, when the jaws are opened to bite, the claws are turned outward, so that their points can be stuck into any thing between the jaws. Fig. 15 is the claw still more enlarged, showing a little hole near the point at a , out of wh

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SPINNERETS.

Fig. 16. The external spinning-organs are little two-jointed tubes on the ends of the spinnerets, Fig. 1 , L. Fig. 16 is the spinnerets of the same spider, still more enlarged to show the arrangement of the tubes. There is a large number of little tubes on each spinneret, and in certain places a few larger ones. Fig. 17 is a single tube, showing the ducta which leads the viscid liquid to form the thread from a gland in the spider’s abdomen. Each tube is the outlet of a separate gland. Fig. 18 ,

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TRAP-DOOR NESTS.

The building of tubular nests is carried to the greatest perfection by certain genera of the Mygalidæ . ( See page 13 .) Atypus , the most northern genus of this family, makes a strong silken tube, part of which forms the lining of a hole in the ground, and part lies above the surface, among stones and plants, Fig. 22 , A. The mouth of the tube is almost always closed, at least when the spider is full grown. Another genus, which lives in warm countries, makes tubes lined with silk, and closed at

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SILK TUBES AND NESTS.

Several species of Theridion and Epeira make tents near their webs, under which they hang when at rest, and in which some species make their cocoons, and lay their eggs. The tents are usually covered outside with leaves drawn together, with sticks or bud-scales collected near by, or with earth and stones brought up from the ground below. Some spiders living on plants make flat tubes, in which they wait for insects, and also hide while moulting, or laying eggs. Others make, especially about the b

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THE WATER-SPIDER.

There is one spider that makes a bag of silk, something like those just mentioned, on water-plants, and lives in it under water, as in a diving-bell; the opening being below, so that the air cannot escape. Mr. Bell, in “The Journal of the Linnæan Society,” vol. i., 1857, describes the filling of these nests with air by the spider. After the nest had been made as large as half an acorn, she went to the surface, and returned, fourteen times successively, and each time brought down a bubble of air,

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COBWEBS.

The simple nests and tubes that have been described are made by spiders, most of which spin no other webs. The larger and better known cobwebs for catching insects are made by comparatively few species. On damp mornings in summer the grass-fields are seen to be half covered with flat webs, from an inch or two to a foot in diameter, which are considered by the weatherwise as signs of a fair day. These webs remain on the grass all the time, but only become visible from a distance when the dew sett

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ROUND WEBS.

These well-known cobwebs are made by the family Epeiridæ , Figs. 1 , 4 ; and the process of making them by the common spider, from which these figures are drawn, can be easily observed in any garden. They generally choose for their web a window-frame or fence, or some such open wooden structure, where there is a hole or crack in which they can hide in the daytime. Fig. 27. Fig. 28. The spider begins by spinning a line across where the web is to be, and attaches another to it near the middle. Sh

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USE OF SPIDER’S SILK.

Various attempts have been made to use the silk of spiders, and chiefly that of the large round-web spiders, for practical purposes, either by carding the cocoons, or by drawing the thread directly from the spider. The latest experiments and plans for this purpose are those of Professor Wilder in “The Galaxy,” vol. viii. He shows how Nephila plumipes might be raised in large numbers, each spider kept by herself in a wire ring surrounded by water, fed with flies bred for the purpose from old meat

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CURLED WEBS.

There is a family of spiders called by Blackwall Ciniflonidæ , see p. 17 , which, besides the usual plain thread, make a peculiar kind of their own. They have in front of the spinnerets, Fig. 33 , an additional spinning-organ called the cribellum, a , a . It is covered with fine tubes, much finer than those of the spinnerets, set close together. Fig. 33. They also have on the last joint but one of the hind-legs a comb of stiff hairs, called the calamistrum, Fig. 34 , on the upper side. Fig. 34.

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THE TRIANGLE SPIDER.

Among those spiders that use the calamistrum is one which makes a web unlike any other. It has been described by Professor Wilder, in the “Popular Science Monthly” for April, 1875, under the name of the “triangle spider.” It lives usually among the dead branches around the lower part of pine and spruce trees, and is colored so like the bark, that when it stands, as it usually does, on the end of a branch, it is easily mistaken for a part of it. The web seems to be made in the night. Wilder saw t

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FLYING SPIDERS.

Often, in summer, the bushes are covered with threads, attached by one end, blowing out in the wind; and bits of cobweb are blowing about, with occasionally a spider attached. To account for such threads, curious theories have been thought of; among others, that spiders are able to force the thread from their spinnerets, like water from a syringe, in any direction they choose. If a spider be put on a stick surrounded by water, she manages, in course of time, to get a thread to some object beyond

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PALPAL ORGANS.

As the male spider gets nearly full grown, the terminal joints of the palpi become swollen, and, after the last moult, the palpal organs are uncovered. Fig. 46. The simplest form of palpal organ is found in the large Mygalidæ , Fig. 6 . It consists of a hard bulb, Fig. 46 , drawn out to a point, in which is a small hole leading to a sac within. Fig. 47. In most spiders the terminal joint is flattened, and has a hollow on the under side, in which the palpal organ is partly concealed. The bulb is

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THE EPIGYNUM.

When the female spider is nearly full grown, there appears a hard, swollen place just in front of the opening of the ovaries, Fig. 1 ; and, after the last moult, the epigynum is uncovered at this place. The epigynum, Fig. 49 , consists of two spermathecæ, E, which connect by two little tubes, H, H, with the oviduct near its mouth, and by two larger tubes, D, with the outside of the spider. The mouths of these larger tubes are often surrounded by various hard appendages to support and guide the p

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USE OF THE PALPAL ORGANS AND EPIGYNUM.

When the reproductive cells of the male spider are mature, he discharges the liquid containing them on a little web spun for the purpose; dips his palpal organs into it, and in a few moments takes up the whole, it is supposed, into the little sacs, Figs. 47 , 48 , inside the bulb; then he seeks the female, and inserts the palpal organs into her epigynum. The soft part at the base of the organ swells up, and presses in the discharge-tube, and probably forces out the contents of the bulb into the

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LAYING EGGS.

When the eggs are mature, the female proceeds, like the male, to make a little web, and lays the eggs on it. Then she covers them over with silk, forming a cocoon, in which the young remain till some time after they are hatched. The laying of the eggs is seldom seen; for the spider does it in the night, or in retired places; and often, in confinement, refuses to lay at all. Fig. 56. The female Drassus , Fig. 56 , spins a little web A across her nest, and drops the eggs E on it, as in the figure.

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ESCAPE FROM THE COCOON.

These cocoons of Argiope are made late in the summer, and the young stay in them till the next season. Out of six hundred cocoons collected by Wilder in the spring, less than a quarter were entire, the rest being pierced, or torn in some way, by birds or insects; so that the spiders were saved the trouble of gnawing their way out, as they can if obliged to. I once noticed a small Theridion gnawing at its soft cocoon, and found that one side had been made in this way much thinner than the rest of

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PARASITES.

The eggs in the cocoon are very liable to be eaten by parasitic insects. Certain wingless Hymenoptera are always hunting around in the neighborhood of spiders’ nests, and may sometimes be seen trying to stick their ovipositor through a cocoon. If they succeed, their eggs hatch before the spiders, and eat the latter up. Other parasites lay eggs on the backs of young spiders, and the larva lives attached to the outside till it gets nearly as large as the spider itself....

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GROWTH IN THE EGG.

The egg of a spider, like that of any other animal, is a cell which separates from the body of the female, and afterwards unites with one or more cells which have separated from the body of the male. This fertilization of the eggs probably takes place when they have reached their full size, and are about to be laid. After the eggs are laid and hardened, it is very easy to watch their development. They grow just as well anywhere else as in the cocoon, and, in order to see through the shell, it is

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YOUNG SPIDERS.

The hatching occupies a day or two. The shell, or rather skin, cracks along the lines between the legs, and comes off in rags; and the spider slowly stretches itself, and creeps about. It is now pale and soft, and without any hairs or spines, and only small claws on its feet; but, in a few days, it gets rid of another skin, and now begins to look like a spider. The eyes become darker colored; marks on the thorax become more distinct, and a dark stripe appears across the edge of each segment of t

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BOOKS ABOUT SPIDERS.

Classification. —Thorell’s “Genera of European Spiders,” in “Acta Regiæ Societatis Scientiarum Upsalensis,” 1869, and Thorell’s “Synonymes of European Spiders,” contain a complete history of the classification of the spiders of Northern Europe, with references to all the descriptions of genera and species, and remarks on the use of names and groups by different authors. The great resemblance between the European and North-American spider faunæ make these the most useful books for American studen

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