The Common Spiders of the United States

by J. H. Emerton

THE GENUS ACROSOMA

These are small spiders, with the abdomen extended back half its length beyond the spinnerets, brightly colored, flattened above, and furnished with several pairs of pointed processes. The cephalothorax is longer than in Epeira and Argiope and widest in the middle. The legs are slender and have only fine and soft hairs. The webs [(fig. 437)] are inclined and have a hole in the middle surrounded by several turns of smooth thread; when hanging in it the spiders look like burrs or seeds. At a slight alarm they will sometimes drop to the ground and hide under the nearest shelter.

Acrosoma mitrata.—This is a smaller species than rugosa or spinea. The abdomen does not extend as far backward as in the other species, but comes farther forward so as to cover half the cephalothorax [(fig. 438)]. The abdomen is truncated behind, with two pairs of pointed processes at the corners, one pair below the other. In front, the abdomen is a little narrowed over the thorax. The legs and cephalothorax are brown, as in the other species. The abdomen is light yellow, darker behind, with two or three pairs of black spots along the middle and five or six dark elongated spots along the sides. The under side is black mixed with yellow spots, as in the other species. Common as far north as Connecticut.

Acrosoma rugosa.—This has five pairs of spines on the abdomen, three pairs in the same places as those of spinea and the other two pairs behind and under the last of the three. All the humps and spines are about the same size. The cephalothorax and legs resemble those of spinea, but the legs are shorter. The colors are white, yellow, and brown in spots and marks like those of spinea, some individuals being almost white, and others as nearly black. The males have a long slender abdomen without humps or spines. This is a common spider as far north as Connecticut, where it is occasionally found.

Acrosoma spinea.—This spider is distinguished from all the common species by the shape of its abdomen, which is narrow in front and has two long spreading points behind [(fig. 440)]. There is a pair of smaller spines on the front of the abdomen and another near the middle of each side. The middle of the abdomen is white or bright yellow. The spines are black at the points and bright red at the base. There are several black spots on the back, and gray marks at the sides. The under side of the abdomen is darker than it is above and marked with black and yellow spots. The cephalothorax and legs are light brown, the thorax with lighter edges. The young have the abdomen longer, with the posterior spines short and blunt. The third and fourth legs are whitish, with dark longitudinal stripes. The males are smaller than the females and resemble the young. The abdomen is a little widened behind and has in place of the spines three pairs of low bumps. The front legs are dark, and the hinder legs light, as in the young. The web [(fig. 437)] has a hole in the middle, across which the spider hangs.

Meta menardi.—This spider lives in caves and similar cool and shady places in various parts of this country and also in Europe. In general appearance, especially when young, it reminds one of Linyphia. The abdomen is longer than wide, high in front, and tapering a little behind [(fig. 445)]. The eyes are near together, the lateral eyes almost as near the middle pairs as they are to each other. The mandibles are long, thickened in front near the base, and slightly turned outward at the ends and strongly toothed on the inner side about the claw. The maxillæ are also long and a little widened at the ends. The dorsal groove is very deep. The legs are long, the front pair twice the length of the body. The full-grown female is half an inch in length, the male a third shorter, but with legs nearly as long. The general color is gray, the lighter parts translucent and yellowish. The cephalothorax has three gray stripes, more distinct in the young, a middle stripe from the eyes to the dorsal groove, and one on each side of the thorax. In the young [(fig. 444)] the markings of the abdomen are two large dark spots near the front end and several other pairs, becoming smaller toward the hinder end. In adults these markings unite into a middle stripe more like Epeira, with a light middle spot in front and several middle spots and pairs of spots diminishing backward. The legs have gray rings at the ends and middle of the joints. The webs are horizontal or inclined, according to the shape of the rocks on which they are built. They resemble the webs of Tetragnatha, having a small central spiral with a round hole in the middle, across which the spider holds herself. This spider matures late in the autumn or early in the summer, and makes large, loose, and transparent cocoons, hung near the webs.

Argyroepeira hortorum.—This is a green and silver-white spider, with slender legs and a long abdomen resembling Tetragnatha. The body of the female is about a quarter of an inch long, the abdomen twice as long as wide, and blunt at both ends [(fig. 447)]. The first pair of legs are twice as long as the body, the second a fourth shorter [(fig. 446)]. The legs are bright green, darker toward the ends. The cephalothorax is green, with a darker stripe in the middle and one on each side. The upper part of the abdomen is silver white, with a dark line through the middle, giving off four pairs of branches at the sides. At the sides of the abdomen are yellow stripes extending downward, and toward the hinder end two bright copper-red spots. The colors of the under side are as bright as those above and are more plainly seen as the spider hangs in its web. The basal joints of the legs are light in color, and the sternum and mouth parts dark. The abdomen is green, darker from front to back, where it is almost black around the spinnerets. In the middle is a large double spot of bright copper red, and the red spots at the end of the body show as plainly from below as from above, and around the middle spot are several small spots of bright yellow. The hairs and spines of the legs are so fine that they do not much affect the general color. On the front side of the femur of the fourth leg there is a fringe of long hairs extending half its length. The males are half as large as the females, with longer and more slender legs and palpi, and the same colors. The webs are nearly horizontal, with a small hole in the center, and under the round web is often a large irregular web. The round web may be a foot in diameter, or it may be so small as hardly to cover the spider. The webs have a large number of rays, and the spirals are very close together, as in the webs of Epeira gibberosa [(fig. 413)]. The smooth central part of the web is circular and very regularly woven, showing usually no trace of the beginning of the temporary spirals, and between it and the sticky circles there is a wide space in which is nothing but the bare rays.

Argiope riparia.—This and the next species are among the largest and most conspicuous of the round-web spiders. It lives among grass and low bushes in open fields and meadows, especially along the borders of ponds and ditches. It matures in the northern states about the first of August. Large females are nearly an inch long, with the front legs longer than the body [(fig. 449)]. The cephalothorax is nearly as wide as long and covered with silvery white hairs, except around the eyes. The front legs are entirely black, and the others are black, except the femora, which are light red or yellow. The abdomen is oval, a little pointed behind and square in front, with two small humps at the corners. There is a black stripe in the middle of the abdomen, narrowed between the humps and widened in the middle, where it includes two pairs of yellow spots. Along the sides are two bright yellow bands or rows of irregular spots. The color underneath is black, with a yellow stripe on the sternum and two wide yellow stripes on the abdomen, with small yellow spots between and at the sides. The young differ considerably from the adults. Until nearly full grown the legs are distinctly marked with dark rings on the ends and middle of each joint. When very young the abdomen is slender, the color is pale, and the markings gray, without the strong black and yellow of the adult. The male [(fig. 450)] is only a fourth as long as the female, similarly colored, but with the markings less distinct and the palpi very large. In the middle of the summer they live near the webs of the females, where they make small and imperfect webs of their own [(fig. 452)]. The females make webs, sometimes two feet in diameter, with a zigzag band [(fig. 448)] of white silk up and down across the middle, and a round thick spot where the spider stands. The inner spiral of these webs is very large, covering a quarter of their diameter [(fig. 452)]. The outer spiral comes very near it, but the spider sometimes passes through the narrow space between them from one side of the web to the other. The web is usually a little inclined, and on one or both sides sometimes has a screen of irregular threads two or three inches distant from it [(fig. 453)], but these are often absent. These spiders have no nest and stand all the time in the center of the web [(fig. 448)]. Sometimes the spider draws away the grass and leaves so as to make an oval opening large enough for the web [(fig. 453)]. In September the eggs are laid in large pear-shaped cocoons with a brown paper-like surface, hung by threads among the grass and bushes [(fig. 454)]. The young hatch during the winter and remain in the cocoon until May. The adult spiders disappear in October and probably all die before winter.

Argiope transversa.—This species is a little smaller than riparia. It lives in the same places and matures a little later, about September 1. The abdomen is more pointed than that of riparia [(fig. 455)]. The ground color is white or light yellow, and is crossed by a great number of black transverse lines, which are sometimes obscured, especially in young spiders, by a thick covering of silvery-white hairs. The cephalothorax is covered with white hairs through which the dark markings on the sides show indistinctly. The legs are light yellow, with black bands at the ends and middle of each joint. The femora of the first legs are sometimes entirely black. The young have the back entirely white. The markings of the under side are similar to those of riparia. The male [(fig. 456)] is colored like the female, but is only a fourth as large. The legs are yellow, marked with black spots, but have no rings. It has the same habits as riparia. It remains in its web later in the season, and makes a cocoon flattened on the top [(fig. 458)] instead of narrowed to a neck, like those of riparia.

This species often makes its web in marsh grass, which it draws away and fastens with silk [(fig. 457)]. As the surrounding grass becomes long and weak, it sometimes falls away, leaving the web in a basket of grass fastened firmly enough together to remain standing.