Part 9

THE GENUS THERIDIUM

The Theridiums are small soft-bodied spiders, making large and loose webs without any large flat sheet of silk, but only a slightly closer portion where the spider stands, or a nest or tent connected with the web. Theridium tepidariorum (fig. 258) and rupicola (fig. 261) live in houses or among rocks, making large loose webs, in which the spider often stands without any covering. They have the abdomen high in front and tapering a little toward the spinnerets. Theridium globosum (fig. 262) has the abdomen of the same shape. The other species are all small and have the abdomen round and brightly colored. They live in more open places on plants, where they make nests in which they are partly hidden, and carry their webs over the neighboring leaves and twigs (figs. 253, 254).

$Theridium tepidariorum.$--This is one of the most common house spiders, and is often found in its webs among rocks, but seldom on plants. The females (fig. 258) measure sometimes over a quarter of an inch in length, but may mature much smaller. The legs of the first pair are nearly three times the length of the body. The male (fig. 259) is shorter and has longer legs. The color varies from dirty white to almost black. The cephalothorax is yellow brown, and the legs light yellow, with brown or gray rings at the ends and the middle of the joints. In the males the legs are orange brown, darker at the ends of the joints. The abdomen is high in front and narrows toward the spinnerets. In dark and well-marked specimens the abdomen has, on the hinder part, six transverse black marks curved upward, thicker in the middle, and partly connected by black spots at the ends (fig. 260). These marks are most sharply defined on the hinder edge, where they are bordered by silver white. The upper mark often forms a conspicuous black and white spot in the center of the abdomen. In light individuals all the markings are smaller and less definite.

It makes a large web in the corners of rooms, under furniture, and in the angles of fences and between stones (fig. 255). It usually stands in the most sheltered part of the web, where a part of it is more closely woven than the rest, but not enough so to conceal the spider. It occasionally makes the web in an open place where there is no shelter above, and then it sometimes carries a piece of leaf into the web and hides under it, as is the usual habit with some allied species. The webs of the young are usually more regular in form than those of adults (figs. 256, 257). A male and female often occupy the same web for a long time. The eggs are laid in brownish pear-shaped cocoons, several of which are made in the same season by one spider and hang in the web. This species is found all over the world.

$Theridium rupicola.$--This resembles closely tepidariorum and is easily mistaken for the young of that species. It does not grow larger than an eighth of an inch long. The colors are like tepidariorum, usually dark gray with black spots, the back of the abdomen sometimes almost white. The legs are distinctly ringed with light and dark. In the middle of the abdomen is a pointed hump, the front part generally black and the hinder part white (fig. 261).

It lives under stones and among rocks, in webs like those of tepidariorum, often containing grains of sand which look as if placed there by the spider, as sand falling into such a web would go through without sticking to the threads.

$Theridium globosum.$--This is another species with a high abdomen like tepidariorum. It is about a twelfth of an inch long and almost as high (fig. 262). The abdomen is a little flattened behind and pointed toward the spinnerets. The hinder part is white, with a large black spot in the middle, below which is sometimes a smaller black spot. Sometimes there is a bright white line around the light area. The front upper part of the abdomen is yellowish gray, and the under part brown. The cephalothorax is orange brown, except a black spot between the eyes. The legs are orange brown.

$Theridium differens.$--Female about one-eighth of an inch long, and the male smaller. The abdomen is round, and the middle stripe often very brightly colored, with white or yellow at the edges and red in the middle (fig. 264). The rest of the abdomen is reddish brown, darkest next to the white edge of the stripe. There are no distinct marks on the under side. In males the stripe on the abdomen is obscure, and the whole abdomen dark reddish brown (fig. 265). Sometimes, especially in young spiders, the abdomen is entirely yellow, with indistinct brown markings. The cephalothorax is orange brown, often darker in the middle, but with no distinct stripe. The legs and palpi are yellow in females and orange brown in males, slightly darker at the ends of the joints. The epigynum has no openings in sight. They are on the inner side in the transverse fold across the abdomen. The palpal organ (fig. 266) has two appendages at the end, one hard and roughened and the other soft. The web is on low plants of all kinds, usually two or three feet from the ground (fig. 263). There is sometimes a small tent, often hardly deep enough to cover the spider, from which the web spreads two or three inches, according to the shape of the plant. The cocoons of eggs are white and nearly as large as the spider, and are attached in the nest.

$Theridium murarium.$--Length about one-eighth of an inch, with the abdomen nearly spherical. The general color is gray. The legs are pale, with dark bands at the end and middle of each joint. The cephalothorax is pale, with a dark line in the middle and one on each side, the middle line sometimes divided into two near the eyes (fig. 267). On the abdomen there is an undulated middle stripe, white at the edges and the front end, and reddish in the middle. On both sides of this stripe the abdomen is nearly black and becomes gradually lighter toward the sides. The sternum is pale, with a black edge and black stripe in the middle. The under side of the abdomen is gray, with a long black spot in the middle and a smaller one over the epigynum. There is little difference in size or color between the sexes. The epigynum (fig. 269) has two round holes, wide apart, near the thickened edge. The palpal organ (fig. 268) is shorter and simpler than it is in differens.

$Theridium spirale.$--This is a round-bodied spider of the same size as differens and murarium. The cephalothorax is orange brown above and below, with an indistinct dark stripe as wide in front as the eyes and narrowed behind. The abdomen has a middle stripe like differens, nearly as wide in front as it is in the middle (fig. 271). The rest of the abdomen is gray, darkest toward the stripe. The legs are pale, sometimes with faint gray rings at the ends and middle of each joint. The middle stripe of the abdomen is sometimes reddish as in murarium, but oftener gray, with a dark spot near the front end. The males (fig. 270) have the same color and markings as the female and are sometimes more distinctly marked. The male palpi (fig. 272) are very large, and the palpal organ has a long tube coiled on the under and outer side. The openings of the epigynum (fig. 273) are about their diameter apart.

$Theridium frondeum.$--White, light yellow, or greenish white, with black markings that are very variable (fig. 274). Usually the cephalothorax has two fine black lines running back from the eyes and uniting behind the dorsal groove, and black edges. The legs are usually darkened with brown at the ends of the joints. The abdomen is large and round, and has on the back a light undulated band bordered by brownish translucent spaces, with two black spots just over the spinnerets. Sometimes there are black spots in the translucent spaces, especially toward the hinder end, and these may be united into two long black stripes. In some individuals of either sex the black on the cephalothorax forms a wide band in the middle, almost covering the back, and a black stripe of similar width extends backwards on the abdomen for half its length. These black-striped individuals have all the other variations of color and markings. The males have all the colors and spots brighter and the legs longer than the females. The mandibles of the male are longer than those of the female and have at the base, in front, a low conical point.

This species is found from the White Mountains to Alabama. In New England it matures in July and is found on bushes all summer.

$Theridium unimaculatum.$--This little species differs in color and markings from all the others, and may almost always be distinguished by the white abdomen, with a black spot in the center of the back. The females are a twelfth of an inch long and the males smaller. The cephalothorax is orange yellow, with a black spot around the eyes, extending back in a point as far as the dorsal groove, and there is also a fine black line along the edges. The legs are orange, lighter in the female and darker in the male, with the first and second pairs in the male much stouter. The sternum is orange, with black edges. This spider makes a web, like the other small species, among small leaves and winters under dead leaves on the ground.

THE GENUS STEATODA

Steatoda has the legs shorter and stouter than Theridium. The abdomen is oval and often a little flattened on the back. It is smooth and shining, the hairs being fine and scattered so as to be hardly visible. The thorax is thick and hard, and in some species marked with hard projections and depressions. The head is generally narrow, and the front middle eyes are in several species larger than the others and farther forward and wider apart. In other species all the eyes are about the same size. The webs consist of a flat sheet supported and held down by threads.

$Steatoda borealis.$--This is a dark reddish-brown spider, quarter of an inch long, living among stones or in the corners of fences and window frames, generally well concealed by its web or nest. The cephalothorax is orange brown and covered with short stiff brown hairs. The head is one-third as wide as the thorax and a little higher, the eyes near together, with the front middle pair projecting forward beyond the mandibles (fig. 279). The legs are brown, with faint darker rings, and are thickly covered with hairs. The abdomen is dark chocolate brown, sometimes without any light marks on the upper side, but usually there is a light line running around the front half and another in the middle, extending back half the length of the abdomen and usually broken into several spots. The four depressed spots on the abdomen are distinctly marked. On the under side there is a light stripe on each side, meeting behind the spinnerets. The sexes are much alike in size and color, but the palpi of the male (fig. 278) are longer than the cephalothorax, and the terminal joint is very large and complicated. The web consists of a flat sheet, held out by threads in all directions, but is often so crowded into a corner that its structure is hard to understand (fig. 276).

$Steatoda guttata.$--Only one-tenth of an inch long. The cephalothorax is high, with scattered hairs, at the base of each of which is a horny ridge. The cephalothorax is dark brown, with the legs lighter and more yellow. The abdomen is nearly spherical and hard at the front end, where there is a ring around its attachment to the thorax. Sometimes the abdomen is bright yellow or orange, without markings on the back, but oftener it is partly brown, with two or three pairs of silvery white spots (fig. 280). The males and females are alike in size and color, and the palpi of the males are very large, as in borealis. They live under stones at all seasons and mature in April and May.

$Steatoda marmorata.$--About a quarter of an inch long. The cephalothorax and legs yellowish brown. Cephalothorax smooth, with a few hairs. Legs covered with fine hair. The abdomen is usually nearly covered by an oblong dark spot darkened at the edges, where it is bordered by silvery white (fig. 283). The middle is lighter, with a central dark stripe. In some individuals the dark markings are broken up into four pairs of black spots partly connected with a middle line (fig. 282). The head is wider and the eyes smaller and farther apart than in the other species, and the front middle eyes are the smallest. The head is wider in males (fig. 284) than in females, and the mandibles larger. It lives under stones and leaves at all seasons and occasionally on bushes.

$Steatoda corollata.$--This, when full grown, is a little larger than marmorata and darker colored, and the legs are shorter and stouter. The cephalothorax is dark brown, and the legs lighter brown, with dark rings at the ends of the joints. The abdomen is yellowish at the sides and has four or five irregular yellow spots, or pairs of spots, along the middle of a dark brown oval patch which nearly covers the middle of the back. In young specimens the abdomen is lighter, with several pairs of dark spots. The eyes are all nearly the same size, the front middle pair slightly larger and farther forward than the others. It lives under stones, like the other species.

$Steatoda triangulosa.$--The female is a fifth of an inch to a quarter of an inch long. The legs are longer and more slender than in the other species, the first pair twice as long as the body. The cephalothorax is orange brown, slightly rough in females and with short ridges at the base of the hairs in males. The front middle eyes are not larger than the others and are not as far forward as in borealis. The legs are light yellow, with slightly darker rings at the ends of the joints. There are thickened brown spots at the base of the hairs all over the body. The abdomen is light yellow, with two irregular brown stripes partly broken into spots and sometimes connected together (fig. 286). The palpi of the male are as long as the femur of the second legs and are small at the end. This spider lives in houses, around window frames and similar places, like borealis. The egg cocoons are white and hang in the web.

$Asagena americana.$--This resembles Steatoda, but the abdomen is longer and flatter, and the whole appearance more like some of the Drassidæ. Like Steatoda, it is usually found with its web under stones. It is about a sixth of an inch long. The cephalothorax is dark reddish brown, slightly rough in the females and with sharp points along the sides in the males. The legs are yellow brown and in the males have two rows of small teeth under each femur. They are stout, as in Steatoda marmorata, and differ little in length. The abdomen is oval and dark brown in color, with two white spots across the middle (fig. 287). The front of the head is rounded and a third as wide as the thorax. The eyes are close together and all about the same size. The males have the cephalothorax larger and rougher, but in size and color resemble the females.

$Latrodectus mactans.$--This is the largest spider of the family. It is sometimes half an inch long, with the abdomen round and the whole body black, except a bright red spot underneath and one or more red spots over the spinnerets and along the middle of the back (figs. 289, 290). The spots turn yellow or white in alcohol. The cephalothorax is about as wide as long, and the grooves between the head and thorax are deep. The lateral eyes are farther apart than usual in this family. The legs of the male are much larger than those of the female, and each joint is orange brown in the middle and black at the ends. The abdomen of the male has a row of red and white spots in the middle line, as some females do, and across the front end, and along the sides four pairs of stripes, red in the middle and white at the edges (fig. 291). The young of both sexes are colored somewhat like the male and, when very small, have very little black on them. The males vary much in size, some being only a quarter as large as the female. This spider makes its nest among loose stones, on plants, or in houses. Around its hiding place it spins a large funnel-shaped tent that widens into a flat or curved sheet of web, closer in texture toward the tube and more open toward the edges, spreading two or three feet over plants and stones. It is found all over the United States, as far north as Massachusetts and New Hampshire and south through Florida, the West Indies, and South America, as far as Chile. It is everywhere feared as poisonous and dangerous, probably on account of its large size and conspicuous colors, as there is no good reason for considering it more poisonous than other spiders.

$Argyrodes trigonum.$--A little yellow triangular spider, with a high, pointed abdomen (fig. 292). Large females measure an eighth of an inch from the head to the spinnerets and nearly as much from the spinnerets to the tip of the abdomen. Seen from above, the end of the abdomen is a little flattened and notched in the middle (fig. 293). In the female the part of the head around the eyes is slightly raised and the lower part of the front of the head carried forward a little beyond it (fig. 294). In the males there are two horns on the head, one between the eyes and one below them (fig. 295). The color is light yellow, sometimes with a metallic luster, as though gilded. On the back of the cephalothorax are three light brown stripes, and sometimes there are dark spots at the sides of the abdomen and over the spinnerets. The legs are slender, without markings, the front pair longer than the others. The point of the abdomen is movable and is sometimes curved downward when the spider is disturbed in the web, as shown by the dotted line in fig. 292. They make webs like those of Theridium, between branches of shrubs (fig. 296) and also among the upper threads of the webs of larger spiders. They have been found in the webs of Agalena, Theridium, and Linyphia, in the looser parts, out of reach of the maker of the web. Hanging in the web, they look like straws or the scales of pine buds that have fallen into it. The cocoons of eggs hang in the web and have a peculiar shape (fig. 296), the upper part conical and the lower part contracted into a narrow neck. The species is common in New England and is found all over the country as far south as Florida.

$Argyrodes nephilæ.$--This is about as large as Argyrodes trigonum, with the hump silver white and the under side of the body black or dark brown (fig. 297). The hump ends in a blunt round point. The front of the head is more nearly vertical than in trigonum, and the upper part projects forward, carrying with it the front middle eyes. In the male there are two horns in front of the eyes, the upper one carrying the middle eyes of both rows (fig. 299). The cephalothorax is black or dark brown above and below. The abdomen is black on the under side, including the spinnerets, and there is a black middle stripe extending back to the tip of the hump. The basal joints of all the legs are white. The third and fourth legs are light colored, with a little brown at the ends of the joints. The second legs are darker, and the first pair are almost black, except at the ends. The males are colored like the females, but have the abdomen not much larger than the cephalothorax (fig. 298), and the hump rounded. This is a southern species and is said to live among the outer threads of webs of large Epeiridæ. It does, however, make webs of its own, and I have seen the adults of both sexes at Charleston, S.C., in these webs away from any other spiders.

$Argyrodes fictilium.$--In this species the pointed hump on the abdomen is much more elongated than in trigonum, in some spiders to eight or nine times the length of the cephalothorax (fig. 300). The tip is rounded in young specimens and sharp pointed in the larger ones. The front of the head is more inclined than that of trigonum (fig. 301). The colors are light yellow and silvery white, with three darker lines on the cephalothorax and a faint middle line on the abdomen. The legs are very slender and long in proportion to the long abdomen. Found rarely from New England to Alabama.

$Spintharus flavidus.$--A sixth to a quarter of an inch long. The cephalothorax is nearly circular, and the head small and narrow like that of Argyrodes, with the hinder middle eyes very far apart. The abdomen is widest across the front third, where it is two thirds as wide as it is long, and from here it tapers to a blunt point over the spinnerets (fig. 302). On the back the abdomen is flat and marked with white stripes each side, and between them a large pattern in black and red, lighter toward the middle, where there are two or three pairs of white spots. The legs are slender like those of Argyrodes, the first and fourth pairs the same length and twice as long as the second pair. The tibiæ of the first and second legs are bright orange color, and the rest, like the cephalothorax, pale yellow. The male has longer legs and more slender abdomen. They live on low plants, and the web is unknown. They have been found from Massachusetts to Alabama.

$Euryopis funebris.$--A little dark-colored spider, with a flat abdomen pointed behind and bordered with a silver-white stripe. It is almost an eighth of an inch long. The cephalothorax is small and as wide as it is long, with the sides rounded. The head is half as wide as the thorax, a little raised and extended forward over the mandibles (fig. 303). The front middle eyes are largest and are farther apart and farther forward than the others. The abdomen is flat and nearly as wide in the middle as it is long, and tapers to a point behind. The general color is black or dark gray. The cephalothorax is yellowish under the abdomen and black in front. The abdomen has a bright silvery stripe around the hinder half, and inside this the color is black, broken by light spots in the middle. The legs and palpi are light yellow, with dark rings on the ends of the joints. The fourth legs are longest. It is shaken from bushes in summer, or from dead leaves on the ground in winter, and its web is unknown. It is found from the White Mountains to Alabama.

$Theridula sphærula.$--This is a very distinct and easily recognized species, although it is less than a tenth of an inch long (fig. 304). The cephalothorax is yellow, with a wide black stripe in the middle. The abdomen is high and round and wider than it is long; it is yellowish gray, with a greenish white spot in the middle and a black spot on a slight elevation at each side. There is also a black spot around the spinnerets. The legs are light yellow. In the male the light parts of the cephalothorax and legs are orange color, and the markings of the abdomen less distinct than in the female. It lives on bushes all over the country.