30 
Psyche 
[March 
(Fuesslin) and Savory (1964) discussed web flexing, dropping from 
the web and death feigning as reflex responses. Robinson and Robin- 
son (1973) ascribed a defensive function to movement by Nephila 
maculata (Fabricius) up the web, sometimes onto nearby vegetation. 
Eberhard (1970) was able to relate dropping from the retreat by 
Araneus cornutus (Clerck) to attack by predatory wasps. 
This study identifies some of the components of predator avoidance 
behavior in Argiope aurantia Lucas and A. trifasciata (Forskal), 
which are known as the black and yellow garden spider and banded 
garden spider respectively. The frequency of occurrence of various 
components is determined for both species; response variation with 
instar and direction of approach by a predator model is assessed. In 
addition, specific aspects of web architecture, barrier webs and sta- 
bilimenta, are examined and the possible relationships to predator 
avoidance behaviors are discussed. 
I wish to thank Mr. David Stair for field assistance, my wife 
Ginny for preparation of the figures and Drs. Susan E. Riechert and 
Gordon M. Burghardt for critically reviewing the manuscript. 
Financial support was provided by the NSF (grant BMS 74- 
17602) and by the Graduate Program in Ecology at the University 
of Tennessee, Knoxville. 
Methods 
During the spring of 1974 a field study of mortality factors and 
migration characteristics of the orb weaver Argiope aurantia was 
initiated in an overgrown, abandoned pasture 2 mi. west of Glendale, 
Loudon County, Tennessee. While engaged in this research, I fre- 
quently observed encounters between the two Argiope species, auran- 
tia and trifasciata , and salticid spiders, Phidippus audax (Hentz) 
and P. clarus (Keyserling) . Some attacks by the salticids were suc- 
cessful, some resulted only in leg losses by Argiope and some were 
unsuccessful. Due to the brevity of these encounters I rarely ob- 
served complete sequences. Thus, in order to obtain quantitative 
evidence concerning the nature of predator avoidance in Argiope, 
an artificial predator was employed. For the purposes of this study, 
a standard-sized lead pencil with rubber eraser (roughly the cross- 
sectional diameter of the salticids) was used to simulate an inverte- 
brate predator. Spiders were approached with the eraser end of a 
pencil from either the ventral surface, in which case the hub of the 
web near the eye region was touched or from the dorsal surface. 
When approached dorsally either the eye region or to a lesser extent 
