Attack behavior of diguetid spiders and the origin of prey wrapping in spiders

Spiders use silk in prey capture in two ways: in the construction of webs which trap and partially immobilize prey, and in wrapping prey. Aerial webs have evolved independently in several families of spiders, including the Araneidae, Uloboridae, and Diguetidae (Kas- ton, 1966). As pointed out by Savory (1952, p. 20), a spider's web greatly extends the area covered by its sense of touch ; it also at least partially immobilizes any prey which encounters it. Thus a web- living spider is more likely to "encounter" a new, partially subdued prey while handling another than is a webless spider. Most prey which become caught in a web will eventually work free and escape unless they are further immobilized. Barrows (1915) found that flies remained in the orbs of Araneus sericatus (Epeira sclopetaria) an average of only 5 seconds. However, most aerial web spinning spiders hang upside down in their webs, and if they dropped a prey which they had already caught while making a new attack, it would fall from the web and be lost. It is probably for this reason that many of these spiders wrap their prey and secure it to the web soon after encountering it, thus freeing their chelicerae for subsequent attacks.