Muscidifurax raptorellus Kogan Legner is a gregarious pteromalid ectoparasitoid that attacks pupae and pharate adults from several families of the higher Diptera. Egg-to-adult development time, adult parasitoid size and emerging offspring (= secondary) sex ratio of hi. raptorellus were compared with clutch size in two hosts that differed greatly in mass, the small Musca domestica Linnaeus and the larger Calliphora vomitoria Linnaeus. The mean number of emerging parasitoids did not vary significantly with host species, although slightly higher clutch sizes were recorded in C. vomitoria. Irrespective of offspring sex, parasitoids completed development more rapidly in M. domestica than in C. vomitoria. In the small host, the development time and adult size of M. raptorellus were negatively correlated with clutch size. By contrast, female parasitoid size was unaffected by clutch size in the larger host, C. vomitoria. Ln both hosts, female parasitoids were significantly larger than male parasitoids. The secondary sex ratio (percentage males) of emerging parasitoids was significantly lower in C. vomitoria, and varied with clutch size in both hosts. In C. vomitoria, the greatest proportion of females emerged from hosts with the highest clutch sizes, whereas in M. domestica hosts with the highest clutch sizes produced the lowest proportion of female progeny. The results described here show that the development of M, raptorellus is profoundly affected by interspecific differences in host quality. Our results suggest that mating structure and host quality have potentially different effects on sex ratio decisions in M. raptorellus, and perhaps other gregarious parasitoids.
Original languageEnglish
Pages (from-to)299-304
Number of pages6
JournalBulletin of Entomological Research
Volume88
Issue number3
Publication statusPublished - 1998
Externally publishedYes

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