Overstinging by hymenopteran parasitoids causes mutilation and surplus killing of hosts

An appraisal of the regulatory role of natural enemies on target pests requires the identification of the mechanisms/traits that enhance the ability of an organism to control the density of its prey/host. After stinging herbivore hosts with their ovipositor, hymenopteran parasitoids tend to reject them without ovipositing or host-feeding. Termed pseudoparasitism, the frequency and consequences of this type of attack (hereafter oversting) have been largely disregarded in the hymenopteran parasitoid literature. We choose the parasitoids Aphytis melinus and A. chrysomphali and their common host Aonidiella aurantii as a model system to study this behavior. Using field and laboratory observations, we showed that overstinging is a common behavior in the wild. Under controlled conditions, overstinging occurred more frequently than host-feeding, a behavioral trait that is used to evaluate the potential of parasitoids as biological control agents. Oversting reduced the fecundity and survival of the herbivore host. When we compared between parasitoid species that attack the same host species, the virulence and frequency of this behavior depended on parasitoid species. These results demonstrate that overstinging should be incorporated in the models of host-parasitoid interactions to analyze population dynamics as well as in the future selection of parasitoids for biological control.