Behavioral Response of a Sit‐and‐Wait Predator to Spatial Variation in Foraging Gain

The orb—weaving spiders Argiope trifasciata and Araneus trifolium were tested for specific behavioral responses to spatial variation in the net rate of energy return. In laboratory feeding experiments with both species, no changes in attack time, capture success, or web design were caused by increased experience with particular prey types. Separate field experiments in enclosures of old—field vegetation were conducted with Argiope trifasciata. Spiders were free to move between four contiguous quadrats which differed only in the ration fed to spiders. Length of stay at a site was positively correlated but probability of moving and distance moved were negatively correlated with ration level. Spiders moved more often than predicted by random expectation when current rations were less than previous rations. These responses produced an aggregation of spiders in quadrats with high ration levels over an 11—d—period. This increase in search intensity which increasing return rate is qualitatively similar to that observed in searching predators in previous studies.