PREY SPECIFICITY IN CHRYSOPA - AN INTERSPECIFIC COMPARISON OF LARVAL FEEDING AND DEFENSIVE BEHAVIOR

To examine pathways in the evolution of prey specialization in insects, we conducted a comparative experimental analysis of larval behavior in two sympatric predacious sister-species (Chrysopa quadripunctata, a generalist, and C slossonae, a specialist on the woolly alder aphid). Responses of the larvae to food (Myzus persicae) and camouflaging material (waxy secretions from woolly alder aphids or exuviae from M. persicae) were quantified during four discrete developmental periods. Our analysis revealed species-specific, ontogenetic, and environmentally induced variation in larval defensive and feeding behavior. The pattem of interspecific variation indicates that larval behavior could have subserved two processes in the evolution of prey specialization in the sister-species' progenitor: establishment on a specific prey and adaptation to the prey. First, the presence of the woolly alder aphid's secretions results in generalist larvae camouflaging themselves to a degree that rivals that of the specialist. Such phenotypic plasticity could have promoted the progenitor's initial adoption of the ant-tended woolly alder aphid as prey and its wool as a source of camouflaging material. Second, quantitative differences between the generalist's s and specialist's behavior indicate that adaptation to the woolly alder aphid did not require the acquisition of novel behavioral traits in the larvae. It involved modifications in the expression of defensive behavior that existed in the generalist ancestor and alterations in the ability to attack and feed on robust prey.