Influence of host distribution on foraging behaviour in the hyperparasitoid wasp, Dendrocerus carpenteri

Abstract

The foraging behaviour of Dendrocerus carpenteri Curtis (Hymenoptera: Megaspilidae), an ectophagous hyperparasitoid of aphidiine wasps inside mummified aphids, was examined in the laboratory with an experimental system consisting of broad bean, Vicia faba L, the pea aphid, Acyrthosiphon pisum Harris, and a primary parasitoid, Ephedrus californicus Baker. Pea aphids parasitised by E. californicus often disperse from their feeding sites (or off host plants) before dying and mummifying. Response of female hyperparasitoids to host distribution was evaluated at two spatial scales. At the first scale, behaviour of hyperparasitoids was examined on individual plants with different densities of hosts. At the second scale, habitat complexity and host location were manipulated in large foraging cages containing several plants. I show that patterns of density-dependent hyperparasitism can result from the foraging behaviour of D. carpenteri. However, dispersal of parasitised aphids may not reduce the incidence of hyperparasitism if hyperparasitoids systematically search the habitat.