THE GENUS ERIGONE

The Erigones are all very small spiders, and for this reason few of them will be described. They live, for the most part, near the ground in grass, moss, and dead leaves, with small webs like those of Linyphia, and are seldom seen unless carefully searched for. There is one season of the year, however, when the Erigones appear in immense numbers. This is during the fine weather that comes after the first frosts in October and November, when they, in company with the young of many larger kinds of spiders, come to the tops of posts and fences and, turning their spinnerets upward, allow threads to be drawn out by ascending currents of air, until sometimes the spiders are lifted off their feet and carried long distances. Though not so easily seen, the same performance is going on at the tops of grass and bushes, and at times the whole country is covered with threads of silk, and the threads in the air tangle together into flakes, which at length fall, sometimes from great heights. This appearance is called in England "gossamer" and in Germany the "flying summer" and the "old woman's summer." Why the spiders spin the thread and what use it is to them to be blown about are unknown. At the time of the autumn flights great numbers of these spiders may be seen on fences and doorsteps in city streets wherever there is a neighboring park or grass plat, and the spiders probably live the rest of the year among this grass near the ground.

Erigone longipalpis and dentigera.—These spiders are a tenth of an inch to a twentieth of an inch long and generally dark brown in color, with the cephalothorax smooth and shining. In some, especially the larger males, the cephalothorax is bright orange and the legs partly of the same color. The females vary considerably in size, but are otherwise much alike. The peculiarities are in the males. The head is about half the length of the cephalothorax and abruptly raised and rounded on the top [(fig. 361)]. Along the sides of the thorax are small pointed teeth of various sizes in a single irregular row [(fig. 362)]. The mandibles are very much thickened in the middle and have a row of teeth on the front outer side [(fig. 364)]. The palpi of the males are sometimes as long as the whole body and of a complicated shape. The femur is curved upward and forward and has a row of little teeth on the under side. The patella and tibia are together about as long as the femur. The patella has at the end a straight tooth directed downward with a short point [(fig. 361)]. The tibia is widened at the end, where it spreads around the base of the tarsus. The maxillæ are much thickened and the bases of the palpi spread wide apart [(fig. 365)]. The palpi are usually carried doubled up in front of the head, with the curved ends of the femora just below the eyes and the palpal organs over the ends of the mandibles. The legs of Erigone are only moderately long, and they walk easily, like the small Drassidæ. They move slowly and are not easily frightened, so that at the time of flying they can be closely watched.

Erigone autumnalis.—This is one of the few species of Erigone that can be distinctly separated from the others. It lives in the same places and is found with longipalpis in the autumn flights. It is only a twentieth of an inch long, but can be distinguished by its light color and bright yellow head. The palpi of the males have the tibia shorter than the patella and the tooth on the patella turned more forward than in longipalpis, with a longer and sharper point tapering from the base to the tip [(fig. 367)].

Ceratinella lætabilis.—This is about the same size as fissiceps,—a sixteenth of an inch long,—but much darker colored, and the males do not have horns or humps on the head. The cephalothorax and sternum are dark brown, and the legs dark orange. The thickened circle on the abdomen [(fig. 368)] is dark orange brown and the thinner parts gray. In the female the thick circle is usually wanting and the whole abdomen dark gray, with lighter spots around the muscular marks. There are also hardened spots around the stem of the abdomen and under the spinnerets in both sexes. The head is slightly elevated behind the eyes, a little more in the male than in the female. The male palpi (figs. [369, 370]) are shorter and stouter than those of fissiceps. It lives in dead leaves and moss, sometimes under stones, and is sometimes found flying in the autumn.

Ceratinella fissiceps.—These little spiders are among the smallest species, measuring only a sixteenth of an inch in length. The cephalothorax and abdomen are short and round, and the abdomen has a round thickened spot on the back, more deeply orange colored than the part around it. The head is black around the eyes, and a black line extends backward half the length of the cephalothorax. The head of the male extends forward over the mandibles, carrying with it the front middle eyes, and above it is a rounded hump with the hind middle eyes. The pairs of lateral eyes are opposite the crease between the humps (figs. [371]). The female has at the same point a slight crease across the head and an elevation before and behind it. They are very common on low bushes in summer and under leaves in winter, and are occasionally seen in the autumn flights.

Cornicularia directa.—The males and females are of the same size and about a twelfth of an inch long. The cephalothorax is brown, varying in different individuals. The abdomen is gray, with the muscular spots lighter than the rest. The cephalothorax is long, narrowing gradually toward the head. In the males there is a slender horn extending forward between the eyes, a little thickened at the end and covered on the upper side with stiff hairs in rows [(fig. 376)]. Under this horn is a smaller one about half as long and close against it [(fig. 375)]. In females the horns are absent, but the shape of the head and arrangement of the eyes are the same, except that the eyes are closer together. There are several other species of Cornicularia, some with similar horns and others with single horns on the heads of the males. They are found under leaves in winter, on plants and fences, and among the flying spiders in autumn.

Ceratinopsis interpres.—Length about a tenth of an inch. Color bright orange, with a little black around the eyes and the spinnerets. In the female the height of the head equals the length of the mandibles, and in males it is greater. The size of the sexes is about the same. The upper middle eyes are a little larger and farther apart than the front middle pair, and between them is a flattened space covered with stiff black hairs, longer in the male than in the female [(fig. 377)]. The male palpi have the femur as thick as the femur of the first leg and the tibia very short and wide, with a little recurved point on the front edge. They live on low bushes in summer and under leaves in winter.