The Influence of Host Deprivation and Host Source on the Reproductive Biology and Longevity of the Squash Bug Egg Parasitoid Gryon pennsylvanicum (Ashmead) (Hymenoptera: Scelionidae)

Laboratory experiments were conducted to determine whether the reproductive biology and longevity of the squash bug egg parasitoid Gryon pennsylvanicum (Ashmead) were affected by (1) host deprivation and (2) host source, i.e., eggs from squash bugs reared on either a susceptible summer squash (Early Prolific Straightneck), or a resistant winter squash (Waltham Butternut), cultivar. Neither the duration nor the schedule of parasitoid oviposition was affected by host availability when G. pennsylvanicum females were deprived of squash bug eggs for intervals of 3 days throughout their adult lives. However, a significantly longer postreproductive period (i.e., the number of days until death after oviposition is completed) occurred in host-deprived parasitoids, but only in those females that emerged from eggs of squash bugs reared on the susceptible cultivar. When reared from squash bug eggs from the resistant cultivar, G. pennsylvanicum had a shorter postreproductive period which did not differ significantly between host-deprived and non-host-deprived females. Fecundity was significantly lower in host-deprived wasps associated with both cultivars than in non-host-deprived female wasps. Dissections revealed no oocyte resorption over the lifetime of 3-day host-deprived females across all treatments. However, when deprived of hosts for 5, 7, or 9 days, morphological changes appeared in the oocytes, suggesting possible resorption.