Host handling and specificity of the hyperparasitoid wasp, Dendrocerus carpenteri (Curtis) (Hym., Megaspilidae): importance of host age and species

The oviposition behaviour of Dendrocerus carpenteri (Curtis), an ectophagou s hyperparasitoid of aphidiine wasps inside mummified aphids was examined. Hyperparasitoids were provided in the laboratory with pea aphids (Acyrthosi phon pisum) which had been parasitized by three different species of aphidi ine wasps (Aphidius ervi, Ephedrus californicus and Praon pequodorum) rangi ng in physiological age from the late larval stage to the late pupal stage. Females accepted only the hosts inside mummified aphids; they ignored live aphids, and did not accept dead, but not yet mummified aphids, although th e latter were sometimes probed with the ovipositor. Female behaviour in han dling A. ervi or E. californicus mummies did not change with experience; ha ndling and oviposition times were stereotypic. However, naive females neede d experience to locate the cocoon of P. pequodorum and distinguish it from the empty aphid mummy. Host acceptance and specificity were influenced more by the developmental stage than the species of the primary parasitoid. In dichotomous choice tests, hyperparasitoids 'preferred' prepupae over younge r pupae of A. ervi, but they did not distinguish between these stages of E, californicus; older pupae were accepted at a low rate. Host preference was not influenced by conditioning on the rearing host. We consider several co nstraints on the host range of D. carpenteri, and discuss alternative expla nations of differential hyperparasitism in the field.