Cornell Nature-Study Leaflets / Being a selection, with revision, from the teachers' leaflets, home nature-study lessons, junior naturalist monthlies and other publications from the College of Agriculture, Cornell University, Ithaca, N.Y., 1896-1904

by New York State College of Agriculture

The Cobweb Weavers.

The webs that we most often find in the corners of rooms are of a different kind and are made by the members of a family known as The Cobweb Weavers. In these webs there is not such a definite sheet of silk as in those of the funnel-web weavers, but instead a shapeless maze of threads extending in all directions. Many of the cobweb weavers, however, make their webs in the fields on bushes, and weave in them a flat or curved sheet, under which the spider hangs back downward. The funnel-web weavers run right side up; the cobweb weavers hang inverted. Some of the cobweb weavers do not remain in their webs, but have a nest in a neighboring crack or corner, from which they rush to seize their prey, and sometimes there is a funnel-shaped tube leading to their nest. But these spiders differ from the true funnel-web weavers in running back downwards on the lower side of their webs.

The Orb Weavers.

The spider webs that most often excite admiration are those in which the supporting threads radiate from a center like the spokes of a wheel, and bear a spiral thread. Such webs are known as orb-webs; and the family of spiders that make them, The Orb Weavers.

Few if any of the structures built by lower animals are more wonderful than these webs; but they are so common that they are often considered hardly worthy of notice. If they occurred only in some remote corner of the earth, every one would read of them with interest.

Fig. 91. Nearly completed orb-web.

The webs or nets of the different species of orb weavers differ in the details of their structure; but the general plan is quite similar. There is first a framework of supporting lines. The outer part of this framework is irregular, depending upon the position of the objects to which the net is attached; but the central part is very regular, and consists of a number of lines radiating from the center of the net ([Fig. 91]). All of these supporting lines are dry and inelastic. Touch them with your pencil and you find that they neither stretch nor adhere to it. Upon these radiating lines there is fastened in a very regular manner a thread which is sticky and elastic. This will adhere to your pencil, and will stretch several times its normal length before breaking. Usually this sticky thread is fastened to the radiating lines so as to form a spiral; but a few species make nets in which it is looped back and forth. And even in the nets where the greater part of the thread is in a spiral there are in most cases a few loops near the lower margin ([Fig. 91]). Examine the next orb-web you find and see whether it is true in that case.

Many of the orb weavers strengthen their nets by spinning a zigzag ribbon across the center. This ribbon is made by spreading apart the spinnerets, the organs from which the silk is spun, and which will be described later. Ordinarily the tips of the spinnerets are held close together so that they form a single thread, but by spreading them apart many threads can be spun at once, thus forming a ribbon.

Some orb weavers are not content with making a simple zigzag band across the center of the net, but weave an elaborate bit of lace in this position. [Fig. 92] is from a photograph of the center of the net of one of these spiders, which was found near Ithaca.