Cues Associated With Patch-Choice Decisions By Foraging Crab Spiders Misumena Vatia

Abstract

I tested the roles of insect prey presence, abundance, and distance in the selection of hunting sites by crab spiders Misumena vatia (Thomisidae) on milkweed inflorescences. Since the inflorescences on a single plant differ in numbers of prey attracted, one can also assess the effect of relative prey abundance on patch choice as overall prey abundance in an area changes. About three-fourths of the spiders chose the inflorescence attracting the most insects on a plant at densities from half to twice the normal prey, and in tests with additional prey presented at close range. Thus they appear to respond to relative prey densities in patch choice, and their accuracy of choice remains constant over a wide range of prey abundance. However, spiders without prey, and ones that had just fed, selected sites randomly. Individuals from all the other experiments left inflorescences, especially high-quality ones, more often as overall prey density increased. This result closely fits a risk-sensitivity model that predicts mobility in choice of hunting site if average prey availability exceeds that required to produce a clutch of eggs.