RISK SENSITIVITY AND THE PARADOX OF COLONIAL WEB-BUILDING IN SPIDERS

Group foraging is rare in spiders, occurring only where prey availabil ity is high. If colonial web-building increases individual prey captur e rates as shown, why does group foraging not occur more often where p rey are scarce? Risk sensitivity may explain this paradox, as variance in prey capture is reduced in groups; risk-averse spiders should join groups only when prey exceed a threshold level. Field studies show th at group foraging varies as predicted between species, between populat ions of a single species, and between sites within a population. Howev er, recent models suggest the necessity of examining variance within i ndividuals over time rather than between individuals within population s. Additionally, mechanisms responsible for variance reduction in colo nial webs may be less effective than previously assumed. New field dat a suggest that while prey variance over time may be somewhat less for individual spiders in groups than for solitaries, the relationship bet ween colonial web-building and variance in prey capture is far more co mplex than originally thought. The influence of risk sensitivity on re productive success and the evolution of colonial web-building is discu ssed.