Muscidifurax zaraptor, a parasitoid of muscoid fly pupae, deposits one egg per host. Discrimination between unparasitized and parasitized hosts minimizes mortality among progeny from superparasitism, the deposition of an egg on a host that has been previously parasitized by a member of the same species. If a wasp deposits one egg in an already parasitized host, the first larva will eliminate the second larva or egg. Females discriminate between unparasitized and parasitized hosts by depositing a marking pheromone that deters subsequent females from attacking the host. A study was conducted to determine if M. zaraptor females can recognize their own previously parasitized hosts to avoid self-superparasitism. It was found that females laid a significanlty greater number of eggs in house fly pupae that had been parasitized by conspecifics (mean number of pupae superparasitized=1.0) than their own previously parasitized hosts (mean number of pupae superparasitized=0.46; F1,25=8.39; P=0.008). Videotaping of oviposition behavior also revealed that females spent significantly more time on pupae parasitized by conspecifics (mean=123.8 mins) than on their own previously parasitized pupae (mean=34.9 mins; t7,7.7=2.64; P=0.031). These results suggest that individual female wasps distinguish their own parasitized hosts most likely by the use of a marking pheromone.
Species 1: Hymenoptera Pteromalidae Muscidifurax zaraptor
Keywords: pupal parasitoid, filth fly
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