Prey-specific foraging tactics in a web-building spider

Predator foraging behaviour can have important impacts on trophic-web structure, and on biological control. In agroecosystems, foraging-tactic selection may determine whether the predator feeds on pest or nonpest prey. We examined the foraging behaviour of a flexibly-foraging web-building spider in response to pest (aphids) and nonpest prey (springtails) aiming to assess the potential role of predator foraging behaviour in biological control. Spiders were allowed to choose between simulated microhabitats with and without a given prey item aiming to determine what tactics spiders would use to forage for the given prey. Spiders preferred microhabitats with aphid prey over paired microhabitats with no prey but showed no preference for springtail prey. Spiders rarely constructed webs in response to aphids but frequently utilized web-construction tactics in the presence of springtails. These findings demonstrate that predators can regulate their foraging activity to maximize the consumption of specific prey items. In the many cases where pest and nonpest prey differ in ecology, prey-specific foraging tactics such as these may limit the usefulness of natural enemies in pest suppression: high-quality, nonpest prey may cause shifts in predator behaviour that reduce consumption of pest prey. Therefore, nonpest prey can have behaviour-mediated, indirect effects on biological control.