Divergent host relationships of males and females in the parasitoid Encarsia porteri (Hymenoptera: Aphelinidae)

"Heterotrophic" parasitoid have been reported in the aphelinid genus Encarsia. These are species in which females develop as primary internal parasitoids of whitefly and males develop as primary internal parasitoids of lepidopteran eggs.The obligate nature of the host relationships in these aphelinids has been questioned and was investigated in this study. We examined the oviposition of female Encarsia porteri (Mercet) in 3 host types: bollworm eggs (Helicooerpa zea (Boddie)), sweetpotato whitefly nymphs (Bemisia tabaci(Gennadius)), and early pupal wasps (E.porteri). Although males Encarsia species develop on wasp pupae as hyperparasitoids, female E.porteri did not generally oviposit in wasp pupae. Whitefly nymphs were parasitized almost exclusively by mated females, whereas both mated and unmated females oviposited in moth eggs. The suitability of the above hosts as well as pupal E. formosa were also investigated for the development of male progeny. Males were produced only on moth eggs. Thus, we conclude that the heterotrophic host relationships of E. porteri are indeed obligate. Larval E. porteri are sexually dimorphic. Early instars of male larvae have a sculptured cuticle, bear long spines along the venter, and have horn-like projections on the head capsule. Females, in contrast, are more typically hymenopteriform with weak sclerotization of the head capsule, indistinct segmentation, and a smooth cuticle. Also, although both male and female early instar larvae are enclosed within a membrane, only female enveloped by an opaque cellular layer within this membrane.