EFFECTS OF PIERIS HOST SPECIES ON LIFE-HISTORY PARAMETERS IN A SOLITARY SPECIALIST AND GREGARIOUS GENERALIST PARASITOID (COTESIA SPECIES)

Host specificity and host selection by insect parasitoids are hypothes ized to be correlated with suitability of the hosts for parasitoid dev elopment. The present study investigates the correlation between host suitability and earlier studied host-finding behaviour of two closely related braconid larval parasitoid species, the generalist Cotesia glo merata (L.) and the specialist C. rubecula (Marshall) (Hymenoptera: Br aconidae). We compared the capability of both parasitoid species to pa rasitize and develop in three Pieris host species, i.e. P. brassicae ( L.), P. rapae (L.) and P. napi (L.) (Lepidoptera: Pieridae). In labora tory experiments, we measured the effect of host species on fitness pa rameters such as survival, development, sex ratio and size of parasito id progeny. The results show that C. glomerata is capable of developin g in the three host species, with significant differences in parasitoi d survival, clutch size and adult weight among Pieris species. The hos t range for development was more restricted for C. rubecula. Although C. rubecula is physiologically able to develop in P. brassicae larvae, parasitoid fitness is negatively affected by this host species, compa red to its most regular host, P. rapae. A comparison of the present da ta on host suitability with earlier studies on host-searching behaviou r suggests that the host-foraging behaviour of both parasitoid species not only leads to selection of the most suitable host species for par asitoid development, but also plays a significant role in shaping para sitoid host range.