The Common Spiders of the United States

by J. H. Emerton

THE GENUS XYSTICUS

In these spiders the general appearance is crab-like. The abdomen is not much larger than the thorax, and both are flat and wide. The first and second legs are a third longer than the third and fourth. The colors are usually various shades of brown and gray, in small spots and bands. On the upper side of each leg is usually a light line, with dark lines on each side of it. The gait is often sidewise, the legs kept close to the ground, so that the spider can move in a narrow crack. They live under stones and bark and leaves, and some, like triguttatus, on low plants. The males have longer legs and smaller abdomen and all the dark markings larger and darker than the females. In triguttatus there is great difference between the sexes, but in most species very little, as in limbatus and stomachosus. The head is generally low, and the four middle eyes form a rectangle a little wider than high [(fig. 97)].

Xysticus stomachosus.—A middle-sized and light-colored species, with gray markings on a light ground, the markings most distinct on the hinder legs and abdomen. The middle of the thorax is lighter than the sides, and there is a small dark spot in the middle and a larger one on each side toward the hinder end (figs. [87, 88]). The third and fourth legs have a distinct dark spot at the ends of femur, patella, and tibia. The abdomen is light, with a few small spots at the front end and three pairs of dark transverse bands on the hinder half. The hairs are short and fine. The male has longer legs and is marked in the same way, with the spots on the abdomen larger and extended farther forward.

Xysticus limbatus.—This is one of the largest species, the females reaching a length of a third to half an inch (figs. [89, 90]). The thorax is one-eighth of an inch wide and nearly as long. The abdomen is a little wider at the hinder end. The legs are short, the longest about half an inch in length. The whole body is hairy. The color is brown, the markings dark on a light ground, best shown by the figures. The middle of the head and thorax is more fully covered by the dark markings than in other species. There is great variation in the color, and young spiders are usually lighter than adults. Adult males and females in June and July.

Xysticus gulosus.—This is a very distinct species and less variable in markings than limbatus and stomachosus. The color is brown or gray, with indistinct darker markings (figs. [91, 92]). The whole body is covered with fine brown spots and has at the hinder end of the thorax and on the legs traces of the same markings that show more distinctly in stomachosus. There are a few transverse dark lines on the hinder half of the abdomen and less distinct longitudinal lines at the sides of the front half.

The male is a fourth smaller than the female, with a smaller abdomen and more slender legs, but the same colors and markings. It is usually found under bark or stones which it closely resembles in color.

Xysticus nervosus.—This is a pale species, the females of which are nearly as large as limbatus. The color is light brownish yellow, with small spots of lighter and darker color scattered all over the body, and there are traces of the markings which are more distinct in other species (figs. [93, 94]). On the hinder half of the abdomen are three or four pairs of very indistinct transverse markings. The legs are marked with irregular dark and light spots, without any distinct rings or markings, and the first and second pairs are darker than the others. In the male the first and second legs are twice as long as the third and longer and more slender than in the other species. It lives on fences and under bark.

Xysticus triguttatus.—This is a small and very common spider living on grass and low bushes. The female is about a fifth of an inch long and the male as large but with a smaller abdomen. The difference in the color of the sexes is so great that they may easily be mistaken for different species. The females [(fig. 95)] are straw-colored, the abdomen almost white, and the thorax and legs brownish yellow. There are three black spots at the back of the thorax and indistinct darker bands at the sides. On the abdomen are two black spots near the front end and three pairs of broken transverse stripes behind. The male [(fig. 96)] has the femora of the two front legs dark brown, the rest like the female or a little darker. The thorax is dark brown, except in the middle, where it is a little lighter, as in the female. The abdomen of the male is strongly marked with transverse black and white stripes, irregular toward the front end.

Xysticus quadrilineatus.—Quarter of an inch long, with the thorax a tenth of an inch wide and the head unusually wide in front. The color is light yellow, with light brown markings and black spots. The cephalothorax has four narrow brown stripes, one on each side close to the edge and the others running back from the lateral eyes [(fig. 98)]; there are also two fine brown lines sometimes extending from the middle eyes to the dorsal groove, but usually broken in the middle. There is a brown spot just behind the dorsal groove and two others in the middle of the cephalothorax. On the abdomen there are two black spots at the front end, two in the middle and two near the hind end, besides several smaller ones along the sides. There are four light brown lines across the hinder half, each with a white line behind it, and at the sides are oblique brown lines alternating with white. The legs have a distinct light line along the dorsal side and are covered with fine brown spots without any other markings.

Xysticus (Coriarachne) versicolor.—The thorax, abdomen, and legs are all much flattened, the head is low, and the upper and lower eyes nearer together than in the other species. The colors are black and gray in irregular spots on a light ground (figs. [99, 100]). On bark or unpainted wood these spiders can hardly be seen. Light individuals have black spots on the legs at the end of each joint and the usual three pairs of dark marks on the abdomen. On the thorax is a white spot in the middle under the front of the abdomen. Around this spot and behind the eyes is black extending in spots along the sides. In dark females and in most males the dark spots are so large that the whole spider is nearly black.

This is a common spider, and a similar species, Coriarachne depressa, is equally common in Europe.