Evaluation of host responses to envenomation as a means to assess ectoparasitic pteromalid wasp’s potential for controlling manure-breeding flies

Abstract

Abstract For most of the pteromalid wasps currently used in biocontrol programs, key fundamental aspects of the wasp’s biology are lacking, including information on the factors that make one fly more attractive than another as a host and which flies are best suited for wasp development, and hence mass propagation for later release. This study examined the physiological relationships between two species of filth flies (Musca domestica and Fannia canicularis) and eight species of ectoparasitic wasps (five solitary and three gregarious species). Seven of eight wasp species preferred the larger pupae of house flies over the smaller F. canicularis, and all solitary species induced death in fly hosts within 24 h after injection of venom. In contrast, the gregarious wasps induced a developmental arrest in parasitized hosts, the duration of which was host species dependent. This host arrest was accompanied by an increase in host hemolymph lipids and correlated with clutch sizes of the two gregarious wasps, Nasonia longicornis and Muscidifurax raptorellus. A similar relationship was not observed for any of the solitary species tested. Isolated crude venoms from all wasps induced similar changes in the morphology of cultured insect cells and the venoms displayed overlapping lethality (LC50s), but the time required for venoms from gregarious species to trigger death was significantly longer than solitary wasp venoms. The possible use of host responses to envenomation as parameters to screen the biological control potential of parasitoids is discussed.