Читать книгу The Common Spiders of the United States - J. H. Emerton - Страница 4

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This book is designed to make the reader acquainted with the common spiders most likely to be found over a large part of the United States as far south as Georgia and as far west as the Rocky Mountains. Local collections show that in the neighborhood of any city in the country there are at least three or four hundred species of spiders; but few such collections have been made, and it is not yet possible to tell all the kinds of spiders that live in any particular place, or how far any species extends over the country. The species which are here described and figured are all of them well known and have been described in other books. Rare and doubtful species are omitted, though some of these may in time prove to be among the most common. A large number of spiders are too small to be easily seen, and most of these are omitted, only a few representative species being described. Spiders have, unfortunately, no common names, except such indefinite ones as "the garden spider," "the black spider," "the jumping spider," and the like. Even "tarantula" has become only a nickname for any large spider. The names of spiders, like those of other animals, have been given to them independently by different persons, so that many of them have more than one name, and the more common the spider the larger the number of names. In this book only one name is usually given to each species, and the name used is one that has been published with a description of the species in some other well-known book. Readers who are interested in the names of species and in comparing the classifications of different naturalists are referred to a "Catalogue of the Described Araneæ Of Temperate North America," by George Marx, in the Proceedings of the United States National Museum, 1890, which is a useful index to what has been published on American spiders.

The front half of a spider's body, called the cephalothorax, contains in one piece the head and thorax, the only outward division between them being shallow grooves from the middle of the back to the front legs. In the middle of the cephalothorax is usually a groove or depression, under which, inside, is a muscle that moves the sucking apparatus by which food is drawn into the mouth. At the sides of the thoracic part are four pairs of legs, and on the head part are a pair of palpi and a pair of mandibles. The legs have seven joints: (1) the coxa, the thick basal joint, having little motion; (2) the trochanter, a short joint moving very freely on the end of the coxa; (3) the femur, the largest joint of the leg, moving with the trochanter in all directions; (4) the patella, moving up and down on the end of the femur; (5) the tibia, joined closely to the patella and moving with it up and down; (6) the metatarsus; and (7) the tarsus, moving together on the end of the tibia. The palpi are like small legs and have one less joint than the walking legs. The mandibles are close together at the front of the head (fig. 2). They are two-jointed, the basal joint stout and the end joint or claw slender and sharp-pointed. The claw has near its point a small hole, which is the outlet of the poison gland. The poison kills or disables the insects which are captured by the spider. Its effect on the human skin varies in different persons; sometimes it has no effect at all; oftener it causes some soreness and itching like the stings of mosquitoes and bees, and cases have been known in which it caused serious inflammation which lasted a long time. Spiders seldom bite, and only in defense, the bites so commonly charged to them being often the work of other animals.

Fig. 1. Diagram of the under side of a spider, with the legs removed except one. Fig. 2. Front of head, showing the eyes and mandibles.

On the front of the head are the eyes, usually eight in number, differing in size and arrangement according to the kind of spider. The sight of spiders is distinct for only short distances. Spiders of middle size can see each other, and the insects which they eat, at a distance of four or five inches, but beyond that do not seem to see anything clearly. At the ends of the feet are two claws, curved and with teeth along the inner edge, and in many spiders there is a third shorter claw between them (fig. 212). The claws are sometimes surrounded by a brush of flattened hairs (figs. 104, 114). The basal joints of the palpi are flattened and have their inner edges extended forward so that they can be used as jaws to press or chew the food. These are called the maxillæ. Between the maxillæ is a small piece called the labium, and between the legs is a larger oval piece called the sternum.

The hinder half of the body, the abdomen, is connected with the cephalothorax by a narrow stem (fig. 1). It has at the hinder end the spinnerets, three pairs of appendages having at their ends a great number of microscopic tubes through which the thread is drawn out. When not in use the spinnerets are folded together, so that the smaller inner pair are concealed.

The thread of spiders resembles that spun by caterpillars in making their cocoons, and can be manufactured in the same way into silk cloth. The spider's thread is composed of a great number of finer threads passing from the body through separate tubes and uniting into one before they have time to dry. This can be seen by examining the attachments of spiders' threads to glass. All the spinning tubes are not alike, but on certain parts of the spinnerets are larger or differently shaped tubes, and these are the outlets of glands of different kinds in the spider's abdomen, and are used in making different kinds of threads for certain parts of the webs, nests, or cocoons.

In front of the spinnerets on the under side is a small opening to the tracheæ, or air-tubes (fig. 1). At the front of the abdomen on the under side is a transverse fold of the skin, at the ends of which are the openings of the air-sacs or lungs, and between them the opening of the reproductive organs (fig. 1). The latter is covered in females by an apparatus, sometimes large and complicated, called the epigynum. Its presence shows that the female is full grown. Young spiders do not have it. Male spiders have the ends of the palpi enlarged, and under the terminal joint what is known as the palpal organ, sometimes very complicated in shape. The presence of these organs shows that the male is full grown. Young males that have nearly reached maturity have the ends of the palpi simply enlarged. Male spiders almost always have the body smaller and the legs longer than females of the same species.

The colors of spiders are partly in the skin itself and partly in the hairs and scales that cover it. Almost all spiders are covered with hair of some kind, but in some species it is so fine and short that it has little effect on the color. In others the skin is entirely covered with hairs of various lengths and sometimes with scales somewhat like those of butterflies, flattened and feathered or toothed on the edges. The colors of spiders are very varied, and in many species, especially of the jumping spiders, as brilliant as those of butterflies. The most common colors are grays and browns, resembling the ground or plants and stones among which the spiders live. Sometimes the color is uniform all over the body, except that it is a little darker toward the head and the ends of the feet. The most common marking is a spot on the front of the abdomen over the spider's heart, sometimes merely a translucent part of the skin and sometimes a definite color spot darker in the middle and outlined with a lighter shade or white. The hinder half of the abdomen is often marked with several pairs of spots, becoming smaller toward the end, and these spots may be united into a pair of stripes or a more complicated pattern. (See figures.) The legs are often marked with rings of color, almost always at the ends of the joints. Besides these common markings there are in some spiders strong contrasts of color, such as bright red or yellow spots on a black ground. In the males, especially among the Attidæ, there are often shining scales that reflect different colors in a bright light, and tufts of black or white hairs about the head and front legs.

Spiders live in all kinds of places. Certain species are attached to houses and seldom found far from them, and many of these occur over a large part of the world. The light webs in the corners of rooms are chiefly the work of Theridium tepidariorum (p. 112), occasionally of Steatoda borealis (p. 119) and Steatoda triangulosa (p. 121). In cellars the thin webs about the stairs and shelves are those of the long-legged Pholcus phalangioides (p. 129) or of Linyphia nebulosa or minuta (pp. 144, 145), and the thick flat webs in corners and between the beams are those of Tegenaria derhamii (p. 96). On the outside of houses live two jumping spiders, the most common being Epiblemum scenicum (p. 60), a small gray species the color of weathered wood, and the other, Marptusa familiaris (p. 61). Some of the round-web spiders live in great numbers about houses. The three brown species, Epeira sclopetaria (p. 160), patagiata, and strix, hide in cracks and at night make their round webs in porches, barns, and bridges. In the northern part of the country Epeira cinerea (p. 165) has the same habit. Epeira globosa (p. 174) is often found on the outside of houses, and so are Zilla atrica and Zilla x-notata (p. 185). Amaurobius ferox (p. 215), a large imported species, is sometimes found in cellars, and several Dictyna (p. 206) live in great numbers on the outside of houses, in corners of windows, under the edges of shingles, or in cracks of walls, spreading their webs wherever there is room for them and gathering dust so that they often make a distinct spot on the wall. In the southern states Filistata hibernalis (p. 220) is one of the most common spiders about houses. Its webs often make a round spot of dust a foot or more in diameter. Stones and sticks lying on the ground furnish shelter for a great number of spiders. Steatoda borealis (p. 119), marmorata (p. 121), and guttata (p. 120) and Asagena americana (p. 122) are found in such places, and so, especially in the South, is Latrodectus mactans (p. 122). The large jumping spiders, Phidippus mystaceus (p. 50) and tripunctatus (p. 51), make large nests of white silk under stones near the ground. The ground spiders, Drassus saccatus (p. 6), Gnaphosa conspersa (p. 2), and Prosthesima atra (p. 5), run on the ground and hide under stones. Lycosa nidicola (p. 69), Lycosa communis (p. 75), Lycosa pratensis (p. 69), polita (p. 70), and cinerea (p. 74) are often found under shelters of this kind. The crab spiders of the genus Xysticus live under stones, but oftener under bark farther from the ground.

In the summer, plants of all kinds from grass to trees are full of spiders. The Lycosas (pp. 68 to 84)run among the short grass. The small species of Linyphia (p. 134) and Erigone (p. 148) make their flat webs close to the ground among small plants. Linyphia marginata, communis, coccinea, and phrygiana make theirs among plants and rocks, a foot or two above the ground. The Theridiums (p. 110) live between leaves and on the ends of twigs, covering them with webs that only show when the dew is on them. Agalena nævia (pp. 91 to 95) makes its flat webs on the grass and anywhere else where it can find a place to fasten them. The jumping spiders (p. 41) run about for their prey on plants, and some of them have silk nests among the leaves. The Misumenas (p. 25) live among flowers and wait for insects to alight within reach. The webs of Dictyna (p. 206) are commonest on the ends of grass and twigs, and are known by the dust that they gather. The round-web spiders mature in the middle of the summer, and then Epeira trivittata (p. 166) is found on all kinds of bushes and grass, and later Epeira insularis (p. 169) and Epeira trifolium (p. 171) in hidden nests near their webs. Epeira angulata, sylvatica, and nordmanni (p. 162) live among bushes and trees. Cyclosa conica (p. 183), Acrosoma spinea (p. 190), and Uloborus (p. 216) live among low bushes in openings of the woods. Hyptiotes (p. 218) lives among the lower dead branches of pines, perching on the end of a twig which it exactly matches in color.

The marshes are the home of great numbers of spiders. The Tetragnathas (p. 198) live there, especially along the streams and ditches. Epeira gibberosa (p. 175) and placida (p. 176) make their horizontal and oblique webs among the tall grass in open places. The two species of Argiope (pp. 193 to 198) swarm in marshes and open fields and in autumn become conspicuous by their size and bright colors, and when they disappear leave over winter their brown cocoons (pp. 197, 200) fastened to the grass.

The moss and dead leaves in the woods are alive with spiders; even in summer some species always live there, and in winter the young of those that in warm weather live among the bushes find shelter where they can remain torpid through the cold season without freezing.

The eggs of spiders are covered with silk, forming a cocoon which varies much in shape and color in different species. Some spiders hang it in the web, others attach it to plants or stones, and others carry it about with them either in the mandibles or attached behind to the spinnerets. The young remain in the cocoon until they are able to run about, and after coming out of the cocoon keep together for a short time, sometimes in a web which they make in common, sometimes in a nest made by the mother, and in some species on the mother's back, but they soon scatter and hunt their own food or make cobwebs, according to the habits of the species.

Different kinds of spiders mature and breed at different times of the year, most of them living only one season. Those that mature late, like Agalena nævia and Argiope, pass the winter as eggs, while those that mature early, like Epeira sclopetaria and Lycosa nidicola, pass the winter half grown. Some species, like Theridium tepidariorum (p. 112), breed several times in the year, and old and young are found at all seasons.

The spiders are naturally divided into two groups of families: (1) the hunting spiders, which run on the ground or on plants, catching insects wherever they find them, or waiting among leaves and flowers until insects come within their reach; (2) the cobweb spiders, which make webs to catch insects and live all the time in the web or in a nest near it.

The hunting spiders include: (1) the Dysderidæ (p. 22), a few species with six eyes only and with four breathing holes at the front end of the abdomen; (2) the Drassidæ (p. 1), or ground spiders, which live among stones and dead leaves or among plants, making tubular nests and flat egg cocoons but no cobwebs; (3) the Thomisidæ (p. 24), the flat and crab-like spiders living on plants or under bark and stones; (4) the Attidæ (p. 41), the jumping spiders, with wide heads and large front eyes, many of them brightly colored and active in their habits; (5) the Lycosidæ (p. 67), the long-legged running spiders, living on the ground and, a few of them, in holes and carrying about their round egg cocoons attached to the spinnerets.

The cobweb spiders include: (1) the Agalenidæ (p. 91, making flat webs on grass or in corners of houses, with a tube at one side in which the spider lives; (2) the Therididæ (p. 107), round spiders with flat or irregular webs in corners and on plants; (3) the Linyphiadæ (p. 134), with flat webs, small spiders of a great number of species living near the ground and in shady places; (4) the Epeiridæ (p. 154), the round web spiders; (5) the Cribellata, having a calamistrum (see p. 205) on the hind legs and making rough webs that gather dust.

Cobwebs are of four principal kinds:

1. The flat webs, closely woven of long threads crossed by finer ones in all directions and connected with a tubular nest where the spider hides, and from which it runs out on the upper side of the web after insects that may fall upon it. These are made by Agalena and Tegenaria (pp. 91 to 104).

2. The net-like webs, made of smooth threads in large meshes, sometimes in a flat or curved sheet held out by threads in all directions. The spider lives on the under side, back downward. These are made by Therididæ and Linyphiadæ (pp. 107, 134).

3. The round webs, made of threads radiating from a common center and crossed by circular loops and spirals, part of which are adhesive.

4. The webs of the Ciniflonidæ, composed in part of loose bands of silk (p. 205).

The simplest and best way to preserve spiders for examination is to put them in alcohol. It kills them immediately and keeps their form and markings and, to a great extent, their colors. They may be kept alive for a few days in glass bottles or jars. It is not necessary to make holes in the covers, or to feed the spiders often. They need water, and this can be furnished them conveniently by putting a piece of wet paper or rag in the bottle.

If one wishes to find what spiders live in his neighborhood, they must be looked for at all times and in all kinds of places. The house and cellar should be looked over and the spiders watched until they are fully grown. The outside of the house and fences should be looked over occasionally in the same way, only those spiders being taken that are full grown, unless they are of new or rare kinds. A great many spiders may be found on the garden fences of a shady street, especially in the early summer and again in the autumn. At both seasons they are more active in the middle of the day and more likely then to be wandering about. The writer always carries two small bottles, one a common homeopathic medicine vial, holding one or two drams and half full of alcohol, the other a straight tube vial, without any neck and about the same size, that is kept always dry and occasionally wiped out to remove the threads that are made in it. The dry bottle is placed quickly over the spider and moved about until the spider is coaxed to go into it. The bottle is then turned up and closed with a finger until the other bottle can be uncorked and the spider shaken into the alcohol. In the fields and along the country roads the stones and sticks that have been lying for some time on the ground should be carefully lifted and searched, both on the under surface and on the ground below. The stones and sticks should be turned back into the same places so that other spiders may find at once comfortable places to hide under. If they are dropped on new ground, it may be a year before they are fit to use again. Among trees and shrubs the best things are to be found by moving slowly about and watching for spiders, nests, and cobwebs without disturbing them. The webs can be best seen when moving toward the light. The greatest number of spiders can usually be found along paths and the edges of woods, and paths through the woods are the best places for many ground spiders.

Spiders should be looked for in the same way in grass, by creeping along on the ground or by sitting down and watching until something walks into view; or the grass and weeds may be swept with a cotton bag, fastened on a hoop like a dip net, with a short handle, and the spiders picked out with a dry bottle from among the leaves and insects that will be gathered with them. Bushes may be swept in the same way, or may be shaken over an open umbrella, or a piece of cloth or paper. In winter, when spiders are torpid, great numbers can be found by sifting the dead leaves that have been lying for some years in the woods. A common coal sieve is fine enough to hold the leaves while the spiders and sticks and dirt pass through, and may be picked over on a cloth or carried home in a bag and examined in the house. The sifting should be repeated several times, as many of the spiders hold to threads among the leaves and become loosened only after much shaking.

In the following pages a general description is given of each family, followed by descriptions of the species belonging to it, with a figure of each species placed as near as possible to the description. In some cases, where the genera are large and well defined, separate descriptions are given of each genus, but where the genus is not easy to distinguish or represented by only a few species, there is no separate generic description, and the species are placed next to those of other genera to which they are most closely related. If the names of spiders are known, they can readily be found by the index at the end of the book. If information is sought about an unknown spider, the illustrations through the book furnish the most convenient index, as the general form and proportions of spiders and the arrangement of their eyes usually show to what family they belong. The ground spiders and those without cobwebs are described first, and the sedentary species living in webs in the last half of the book. Readers unfamiliar with the subject are advised to read first the descriptions of the families and compare with them the spiders that they find in their own neighborhoods. The figures are in most cases enlarged for the sake of distinctness, and spiders of much smaller size must be looked for.

THE COMMON SPIDERS