This group comprises several families that differ greatly in form and habits, but agree in having peculiar spinning organs, different from those of all the other spiders. They have the usual six spinnerets and in addition the cribellum (fig. 469), a flat, wide spinning organ, close in front of the other spinnerets and covered with finer spinning tubes. Besides this additional spinning organ they have on the hind legs the calamistrum (fig. 470), a row of hairs that is used to draw out a loose band of silk from the spinnerets. Most of our species belong to the genera Dictyna and Amaurobius and resemble Tegenaria (pp. 96-99) in their feet with three claws, in the arrangement of the eyes, and in their general form and color. The others belong to the small and peculiar genera Filistata, Hyptiotes, and Uloborus.

THE GENUS DICTYNA

The Dictynas are all small spiders, not more than a sixth of an inch in length, but are brightly colored and live in webs in open places, where they cannot fail to be seen by any one who looks for spiders. They are not easily frightened, and so their habits can be more easily watched than those of many larger kinds. The heads are high, arching up from the eyes to the highest part opposite the first legs (fig. 476). The eyes are higher and the front of the head is more nearly vertical than in Amaurobius (fig. 489). The head is about half as wide as the thorax and distinctly marked off from it and usually lighter colored. The abdomen is sometimes marked with light yellow on a gray ground, as in Amaurobius, or with a light middle stripe of various shapes, bordered with brown or gray (fig. 487). The whole body is covered with fine hairs, and there are often long white hairs in rows on the cephalothorax. The cribellum is large for the size of the spiders and can generally be plainly seen just in front of the other spinnerets. The calamistrum is not so easy to see, but it covers about half the length of the fourth metatarsus. The peculiarities of the species of these spiders are more strongly marked in the males. The mandibles of both sexes are long and a little curved forward at the ends (fig. 476), but in the males they are sometimes so long that the distance from the ends of the mandibles to the top of the head is as great as the length of the cephalothorax, and the lower ends are turned forward at a sharp angle with the upper part. The mandibles of the males are curved apart in the middle, and they have at the base a short tooth projecting forward (fig. 477). The palpi of the males have a process on the tibia, usually near the base, on the end of which are two spines (fig. 478). There is not much difference in size between the sexes, but they are often very differently colored, and the males do not have the cribellum and calamistrum, or have only rudiments of them.

Some species live on walls and fences, making large webs that become conspicuous from the dust which they collect. Others prefer the tops of plants like stiff grass and the tops of golden-rod and spirÆa. Others, like volupis (fig. 474), prefer leaves and the ends of growing branches. The webs are usually irregular, but sometimes are nearly round and formed by threads radiating from the spider's hole, crossed irregularly by other threads (fig. 471).

Dictyna volupis.—This species and frondea are brighter colored and more slender than muraria and volucripes (fig. 484) and live among the leaves of bushes. The female volupis has the legs pale, almost white, and the cephalothorax light brown, darker at the sides and light on the head (fig. 474). The abdomen is yellow in the middle and brown, sometimes red, at the sides. The middle yellow portion forms a regular figure differing much in different individuals. The male is quite differently colored. The cephalothorax, which is larger, is bright orange brown, without much difference between the head and the sides (fig. 475). The legs are light orange, darker than those of the female. The abdomen is dark reddish brown, sometimes over the whole back, but usually with a yellow irregular middle spot smaller than that of the female. The ends of the male palpi are dark colored and as large as the spider's head (fig. 475). The hairs are very fine and light colored and do not modify the color as much as they do in the brown species. The length of volupis is not over an eighth of an inch. The abdomen is oval and not as wide or high as in volucripes and muraria. The head of the male is high, and the mandibles almost as long as the cephalothorax (fig. 476). The lower half is turned sharply forward and flattened out at the end. The mandibles are light orange brown, so that their shape is more readily seen than in the dark species. The tooth on the front of the base of the mandibles is very large in this species (fig. 477).

Dictyna frondea.—This resembles volupis and is likely to be mistaken for it. It is a little smaller, not over a tenth of an inch long, and there is less difference between the sexes. The legs are pale, and the cephalothorax light brown, lighter on the head. The abdomen is gray at the sides, not as red as in volupis, and the middle light stripe is narrower and not as bright yellow (fig. 479). The sternum and under side of the abdomen are gray, as dark as the upper part and sides, while in volupis they are generally lighter. The males have the cephalothorax larger, and that and the legs a little brighter colored than in the female, and the abdomen darker. The mandibles are not as long as in the male volupis, and the ends of the male palpi are much smaller and the tibia longer and straighter than in volupis (fig. 481).

Dictyna cruciata.—About a tenth of an inch long, with the abdomen large and oval, as in muraria. The cephalothorax is light brown above and below, and the legs the same color, but still lighter. The abdomen is gray beneath and at the sides, and silvery white on the back, sometimes over the whole upper surface, but oftener in a stripe widened in the middle so as to form a white cross on a gray ground (fig. 482). The males are darker colored, with the light spot on the abdomen smaller. The male palpi are short and slender, the ends large and rounded and carried close to the head (fig. 483).

Dictyna volucripes and muraria.—These two gray spiders are the common Dictynas on walls and fences and on the ends of grass and weeds, where they make webs shaped according to the places where they live, having in some part of the web a hole in which the spider usually hides (fig. 473). Some allied species make nearly circular webs on walls, with the hole near the center, and gather so much dust as to appear like a spot of dirt (fig. 471). Volucripes is about a sixth of an inch in length, and muraria an eighth of an inch. Volucripes is browner in color and more common on plants, and muraria is grayer and more common on fences. Both species are marked much alike. The cephalothorax is dark brown, partly covered with light gray hairs, some of which form roughly three stripes on the head. The abdomen is large and round, in some females nearly as wide as long. The front half has a middle dark spot of various shapes, and the hinder half two rows of spots connected in pairs with a middle line, forming a figure much like the markings of several species of Epeira (figs. 484, 487). The legs are dark gray or brown, covered with fine hairs, the first pair not much longer than the body. In the females the mandibles are a little thickened in the middle. In the male they are elongated and turned forward at the ends and curved apart in the middle, and have a small tooth on the front near the base. The palpi of the males (figs. 485, 486) are short, with the patella as wide as it is long and wider than the femur and tibia. The tarsus is half longer than wide and pointed at the end. In the tibia there is a little difference between the species that can be seen by looking at the palpi from the side; in volucripes there is a stout process at the base as long as the tibia itself and pointing upward at a right angle with it (fig. 485); in muraria the corresponding process is short and turned forward, and the tibia seems proportionally longer (fig. 486). The cribellum in both these species is large and can easily be seen in front of the other spinnerets. The calamistrum extends over half the length of the fourth metatarsus, which in volucripes is slightly curved.

Amaurobius sylvestris.—This is the common Amaurobius all over the northern part of the country. It resembles our species of Tegenaria (figs. 228, 233) and may easily be mistaken for them. It does not have long upper spinnerets like Tegenaria, and the eyes are lower on the front of the head. The females (fig. 489) are two-fifths of an inch long, and the males a third of an inch, but with much longer legs. The head of the female is almost as wide as the middle of the thorax, and the eyes cover half its width. The front row of eyes are within their diameter of the front of the head. The head is low in front and higher halfway between the eyes and the dorsal groove. The mandibles are much swelled at the base in front, as they are in Tegenaria medicinalis. The abdomen is oval, widest behind, and usually as long as the cephalothorax or longer. The legs are not more than a fourth longer than the body, and slender for so large a spider. The cephalothorax is dark brown, darkest in front, and the legs are a little lighter brown, without markings. The abdomen is gray, with a double row of oblique yellow or white markings on the hinder half and two curved marks of the same color on the front. These spots sometimes run together, so that the whole middle of the abdomen is light colored. The males have the head narrower and the thorax wider and all the legs longer than the female, and the cephalothorax and mandibles are not so dark colored. The male palpi have the patella as short as wide, and the tibia very short and wide, with a short hook on the outer and a longer and more slender one on the inner side, as shown in fig. 490. The epigynum has a small middle lobe inclosed by two lateral lobes that meet behind, and by this the female can be distinguished from the next species,—Amaurobius ferox. The cribellum (fig. 469) is sometimes covered by a fold of the skin, so that it is not readily seen. The calamistrum (fig. 470) is a close row of curved hairs on the upper side of the fourth metatarsus, about half its length. In the male the cribellum is rudimentary, and there is no calamistrum.

This spider makes a large loose web under stones and sticks (fig. 488). In the parts freshly made the loose bands of silk can be seen running irregularly about on the other threads (fig. 491).

Amaurobius ferox.—This lives in houses and is probably an imported species, as it is more common in Europe. It grows a little larger than sylvestris (fig. 489), and the head is a little more narrowed in front of the legs. The colors and markings are much as in sylvestris, but the abdomen is often darker, and the middle light stripe on the front more distinct. The epigynum has a larger middle lobe, and the lateral lobes are straighter and do not meet in the middle. The males are colored like the females and have the thorax wider and the legs longer. The palpi of the male have the tarsus short and round. The tibia (fig. 492) has only a small short hook on the inner side, and a large blunt process on the outer side. The male palpi and the epigynum distinguish these easily from the last species.

Amaurobius (Titanoeca) americana.—Quarter of an inch long and deep black, except the cephalothorax, which is dull orange color, but covered, like the rest of the body, with long black hairs (fig. 493). Some individuals have a few light gray spots in pairs on the abdomen. The shape of the cephalothorax and abdomen are like Amaurobius sylvestris, and the legs are of the same proportional length and stouter. The palpi of the female have the tibia and tarsus a little thickened. The metatarsus of the fourth legs has the calamistrum more distinct than in others of the family, and the metatarsus appears thicker up and down than it is sidewise. The male has the legs longer, particularly the first pair, of which the tibia and metatarsus are more elongated than the other joints, and have many small spines on the under side. The male palpi have the tarsus large and round, supported by a wide and very complicated tibia. It lives under stones in the hottest and dryest places.

Uloborus plumipes.—Uloborus makes a round web, like those of the EpeiridÆ, and when hanging in it resembles a Tetragnatha. The adult female is about a quarter of an inch long, and narrow like Tetragnatha. The cephalothorax is low in front and extends forward, in the middle, beyond the mandibles, and the back part is widened and swelled up on each side where the abdomen extends over it (fig. 494). The abdomen is slightly notched in front and covers the cephalothorax a quarter of its length. The abdomen is widest and thickest in the front third and has there a pair of humps. The eyes are in two rows, those of the upper row largest and on the top of the head, with the lateral pair farthest back. The front row are on the edge of the head close to the mandibles. The first pair of legs is the longest and is twice as long as the second. It has at the end of the tibia a brush of long coarse hairs. The colors are various shades of brown, from very light to almost black. The cephalothorax has a light middle stripe. The legs have the joints light in the middle and black at the ends, except the first leg, which sometimes has the tarsus and metatarsus white, and the rest of the leg dark brown. The fourth metatarsus is curved in on the outer side, where the calamistrum is placed. The male is smaller than the female, the legs are longer, the abdomen is smaller and less distinctly humped, the first legs do not have the brushes on the tibia, and the fourth legs do not have the calamistrum. The webs resemble those of Epeira and Tetragnatha, and are horizontal or inclined. They are often left unfinished, with several turns of the wide temporary spiral still in them (fig.495). Sometimes there are zigzag lines of loose silk across the center or in a middle spiral, and when the eggs are laid the long cocoons are fastened in a line of silk across the web (fig. 497). When this is done the center of the radii of the web is usually at the upper part, instead of in the middle, and the whole web is one-sided. It is found all over the country, usually in shady woods, in bushes, or in the lower branches of trees, especially in the lower dead branches of pines.

Hyptiotes cavatus.—This peculiar spider resembles in shape and color the end of one of the dead pine branches among which it lives. It is a sixth of an inch long. The cephalothorax is as wide as long, highest in the middle, and hollowed behind under the abdomen. The abdomen is oval, thickest behind, and flattened in front, and has on the back four pairs of slight elevations, on which are a few stiff hairs (fig. 498). The legs are short and thickest in the middle, tapering toward the claws. The hind metatarsi are curved in at the calamistrum (fig. 499). The eyes are arranged as in Uloborus, but are farther apart and farther back on the cephalothorax. The male is half as large as the female, the abdomen smaller, and the humps lower.

The web (fig. 500) consists of four rays crossed by a dozen or more threads. The point where the rays meet is attached to a thread which extends to the spider's roost, usually the end of a twig. Here it holds on by the hind feet and draws the thread tight with the fore feet. When an insect strikes the web the spider lets go with the hind feet and is jerked forward by the contraction of the web, and slides along toward its center, where it finds the prey and takes it out of the web to its perch. The making of this web has been described by Wilder in the Popular Science Monthly in 1875. The cross threads are made separately, beginning with the longest. They are begun on the upper ray, the spider walking toward the center, combing out the threads with its hind legs, until it reaches a point where it can cross to the next. It is found all over the country, usually in the pine woods.

Filistata hibernalis.—One of the most common house spiders in the southern states, making webs in corners and on walls and fences (fig. 501). The body is about half an inch long, but the legs are so long and stout that it appears much larger. The first leg, which is the longest, is about twice the length of the body. The palpi are as long as the cephalothorax and thicker than in most spiders. The maxillÆ are inclined toward each other so that they meet in front of the labium. The cephalothorax is flat and narrowed in front between the palpi, and the mandibles are small. The eyes are in one group, close together. The color is dark gray, without any markings, and the whole body is covered with fine short hairs. The calamistrum is very short, and near the base of the fourth metatarsus, where it can easily be seen. The web is like that of Dictyna, radiating irregularly from the spider's hiding place, and when this is on a flat wall forms sometimes a circle a foot or more in diameter, which becomes filled with dust and is enlarged and thickened as the spider grows.