36 
Psyche 
[March 
Predator Avoidance Components 
All descriptions of predator avoidance components apply equally 
to A. aurantia and A. trifasciata. There are differences in relative 
usage of these components (discussed in next section) and their com- 
bination in behavioral sequences. 
Web Flexing 
Web flexing is accomplished when the spider sets the web in motion 
along its short axis by rapid extension and retraction of the legs. 
Spider and web thus swing back and forth parallel to the ground 
surface, since the long axis of the web is oriented more or less per- 
pendicular with respect to the ground. Web flexing adds another 
dimension to the predator’s attempt at attack, that of motion. Ob- 
viously, contact is more difficult to establish and maintain when the 
spider and web are in motion. In one encounter of a salticid and an 
Figure 2. Juvenile A. trifasciata with barrier webs. Note primary bar- 
rier behind dorsum of the spider; arrow is pointing to spider’s dorsum. 
