A possible mechanism for the physiological suppression of conspecific eggs and larvae following superparasitism by solitary endoparasitoids.

Competition for possession of a host by internal solitary parasitoids has been attributed to physical combat and physiological suppression, but the mechanisms that result in what has been referred to as physiological suppression is poorly understood. Some insights are provided by the studies reported here using the solitary endoparasitoid, Campoletis sonorensis (Cameron). Embryos of C. sonorensis less than ten hours old rarely hatch in various artificial media, while embryos twenty hours or older generally hatch. These results suggest that young embryos in which the embryonic membranes have not yet formed are only able to develop in a narrow range of environments represented by the nonparasited hemolymph. In contrast, embryos in which the embryonic membranes are formed are able to develop in a wide range of environments represented by parasitized hemolymph which has been shown by a number of studies to change. These ideas were given support by studies reported here, where young and older eggs were incubated singly or paired. We suggest the general changes in the hemolymph of a parasitized host become unfavorable for the development of newly oviposited eggs.