PREDATOR AVOIDANCE BEHAVIORS AND 
WEB DEFENSIVE STRUCTURES IN THE 
ORB WEAVERS ARGIOPE AURANTIA 
AND ARGIOPE TRIE ASCI AT A 
(ARANEAE, ARANEIDAE)* 
By Wayne W. Tolbert 
Graduate Program in Ecology, University of Tennessee, 
Knoxville, Tenn. 37916 
Introduction 
Many spiders spend virtually all of their lives on orb webs. Orb 
weavers are known from all continents except Antarctica, as well as 
many island groups. In addition to a cosmopolitan distribution, in- 
dividual species are locally abundant in a variety of habitats. The 
diversity of this assemblage is also quite pronounced with 2500 
species of Araneidae, 150 species of Uloboridae and over a dozen 
species of Tetragnathidae recognized (Levi and Levi, 1968). Since 
the uloborids are not closely related to the other two orb-weaving 
families, the ability to construct orb webs probably evolved inde- 
pendently (Kaston, 1966). It is generally conceded that the orb 
web is a highly developed type of spider web (Kaston, 1964) which 
allows exploitation of aerial food sources (insects and other inverte- 
brates), not readily available to other spiders, with a minimum of 
wind damage to the web. Despite the apparent success of this web 
type, it allows exposure of its occupant not only to the exigencies of 
the abiotic environment but to predators and parasites as well. Orb 
weavers fall prey to wasps (Muma and Jeffers, 1945; Kurczewski, 
1963; Kurczewski and Kurczewski, 1968a, 1968b and Dorris, 1970), 
birds (Robinson and Robinson, 1970 and Royama, 1970) and other 
spiders (Enders, 1974). Vertebrate predators such as frogs, toads 
and lizards may be locally important. 
While predator avoidance behaviors have been examined in several 
animal groups (Tinbergen, 1969 and Eibl-Eibesfeldt, 1970), no 
formal study has been completed on spiders. Several earlier spider 
workers (Bristowe, 1941 and Comstock, 1940) noted that web 
flexing, dropping from the web, color changes and other behaviors 
were elicited when spiders were disturbed. Gertsch (1949) listed 
some escape responses of the line weaver Pholcus phalangioides 
*Manuscript received by the editor January 25, 1975 
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