THE EPEIRIDÆ

The Epeiridæ are the makers of the familiar round cobwebs. Like the Therididæ and the Linyphiadæ, they live always in their webs or nests back downward or, when in the round web, head downward. The cephalothorax is generally short, as in Therididæ, and low and wide in front, with the eyes near the front edge, the lateral pairs close together and farther from the middle eyes than the latter are from each other. The mandibles are large and strong. The maxillæ are short, often as short as wide, and parallel or a little divergent and rounded at the ends, never pointed or turned inward. The labium is shorter than wide and rounded or slightly pointed at the end. The legs are usually long and, more commonly than in the other cobweb spiders, stout and furnished with spines.

Most of the common species belong to the genus Epeira and its allies, having rounded abdomens and stout legs, some of them with humps and spines and peculiar angular forms of the abdomen. The colors are often bright, and those of the abdomen arranged in a triangular or leaf-shaped pattern. In Meta (p. [190]) and Argyroepeira (p. [191]) the abdomen is more elongated and the form and marking more like Linyphia. In Tetragnatha (p. [201]) the whole body is long and slender, the abdomen several times as long as the cephalothorax, and the maxillæ and mandibles, especially in the males, much elongated. The colors are more uniform and the markings faint, usually light gray, yellow, or green, like the plants among which they live. The round webs of the Epeiridæ consist of a number of radiating lines, varying in different species from a dozen to seventy, crossed by two spirals,—an inner spiral that begins in the center and winds outward, and an outer spiral that begins at the edge of the web and winds inward. The inner spiral is made of smooth thread like the rays, and dust will not stick to it. The outer spiral is made of more elastic and sticky thread, which, when it is fresh, is covered with fine drops of a sticky liquid. In the finished web (figs. [379], [380]) the outer spiral covers three-quarters or more of the diameter and the inner spiral a quarter or less, but in the unfinished web [(fig. 381)], before the sticky thread is put in, the inner spiral covers nearly the whole of it and is cut out, piece by piece, to make room for the outer spiral.

In beginning a web, after the radiating threads are finished, the spider fastens them more firmly at the center and corrects the distances between them by several short, irregular threads [(fig. 379)] and then begins the inner spiral with the turns, at first close together and then widening, in some species gradually, in others suddenly, until they are as far apart as the spider can reach with the spinnerets on one and the front feet on the next, and so goes on nearly to the outside of the web, where it stops abruptly [(fig. 381)]. The spider usually rests a moment and then begins, sometimes at another part of the web, the outer sticky spiral. In the outermost parts of the web it usually forms several loops [(fig. 381, b to f)], filling in the corners until it approaches the inner spiral and finds room to pass completely around the web. As soon as the inner spiral is found in the way a part of it is cut out, and by the time the outer spiral is finished the inner is reduced to the small and close portion near the center.