The Therididæ are the builders of the loose and apparently irregular webs in the upper corners of rooms, in fences and among rocks, and between the leaves and branches of low trees and bushes. They are generally small, soft, and light-colored spiders, with the abdomen large and round and the legs slender and usually without spines. The eyes are all about the same size and in two rows across the front of the head, with the lateral eyes of the two rows near together and often touching each other. The mandibles are weak and without teeth at the end. The maxillæ are pointed at the end and turned inward toward each other. Most of the Therididæ live always in their webs, hanging by their feet, back downward. The webs have in some part a more closely woven place under which the spider stands, sometimes in the middle of the web, sometimes in a corner out of sight. Where the spider's usual standing place is without other shelter, it is often concealed by pieces of leaves or sand carried into the web by the spider, and sometimes made into a tent. The outer part of the web is usually loosely made in large meshes, but is sometimes in a distinct sheet spreading from the nest and held out by threads in all directions. The cocoons are round and soft and hang in the web, several being made in the same season by one spider.

Several of this family, like Spintharus and Euryopis, have the abdomen smaller and flatter than usual and the fourth legs longer, so that they are better fitted for walking. They are found on plants, and little is known about their webs.

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]).