Superparasitism in gregarious hymenopteran parasitoids : ecological , behavioural and

Superparasitism in gregarious wasps occurs with the deposition of a clutch of eggs by a female into a host already parasitized by itself or a conspecific female. This review synthesizes and interprets the available results in the literature reported from field studies, and from behavioural and physiological investigations. To study superparasitism at the ecosystem level, methodological issues have to be solved to determine threshold values beyond which multiple offspring can be indis- putably classified as originating from superparasitism. This life strategy is then dis- cussed from the parasitoid’s perspective, considering time and egg limitation, host discrimination, clutch size, offspring body size and sex ratio, as well as develop- ment time and survival rate of offspring, with special emphasis on physiological facilitation and constraints. Then, superparasitism in gregarious species is evaluated from the host’s angle, addressing host survivorship and development, host food con- sumption and growth. Although superparasitism may be beneficial for either the first or the superparasitizing female, depending on the system, it is detrimental for both of them under conditions of extreme superparasitism. Recent methodological and experimental advances encourage further studies on the adaptive host choice under field and laboratory conditions, as well as on mechanisms underlying success of the first or the superparasitizing female and their progeny.