Host Influence on the Laboratory Production of the Parasitoid,Microctonus aethiops(Nees)12

The effects of Hypera postica (Gyllenhal) size, sex, and age on the productivity of its parasite, Microctonus aethiops (Nees) (Hymenoptera: Braconidae) were studied in the laboratory. Host size had no significant effect on the mean number of progeny or mean percent females produced per parasitoid. However, host mortality was significantly higher among the small hosts. Host sex had no effect on host selection by the parasitoid, nor was a differential mortality observed between male or female hosts. Host age was a factor in the production of M. aethiops progeny. The majority of parasite larvae diapaused in 1- to 21-day-old host weevils, with the exception of those 7 days old. In the 7-day-old host, 28.5 of a mean 40.5 parasitoid larvae completed development without diapause. In 28- to 70-day-old hosts, with exception of those 49 days old, the majority completed development without diapause. In the 49- to 70-day-old weevils, significantly fewer eggs were oviposited by the parasitoids. This was attributed mainly to the weevils' reduced physical activity and feeding. Parasitization by M. aethiops caused negligible mortality prior to parasite emergence in the 1- to 70-day-old weevils. The results suggest that physical development of the hosts' reproductive organs is not always an accurate index of its suitability for parasitoid development. In general, 28- to 70-day-old weevils were suitable for uninterrupted, nondiapausing development of M. aethiops larvae.