ATTACK BEHAVIOR OF DIGUETID SPIDERS AND 
THE ORIGIN OF PREY WRAPPING IN SPIDERS 1 
By William Eberhard 
Biological Laboratories, Harvard University 
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. 
Araneids and uloborids spin orb webs and use silk extensively to 
immobilize prey. Diguetids spin less highly organized webs, and 
never use silk in prey immobilization. However, they often apply 
silk to prey already subdued by biting. This paper shows how post- 
immobilization prey wrapping may have led to the use of silk as an 
attack weapon by the orb weavers. 
I observed the following species attacking prey: Aphonopelma sp. 
(Theraphosidae, various ages, both sexes), Metepeira labyrintha 
(Hentz) (Araneidae, various ages, both sexes), Argiope trifasciata 
(Forskal) (Araneidae, females of various ages), Uloborus diverms 
Research supported by a grant from the Committee on Evolutionary 
Biology at Harvard, publication by Public Health Service Research Grant 
AI-01944 to Dr. H. W. Levi. I wish to thank Mr. Frederick Shepard, Mrs. 
Lorna Levi, and Drs. M. J. West and F. M. Carpenter for help in pre- 
paring this paper. This work was done under the direction of Dr. H. W. 
Levi. 
Manuscript received by the editor August 1, 1967 
173 
