Biotic and abiotic factors involved in diapause induction of the parasitoid, Aphidius nigripes (Hymenoptera: Aphidiidae)

Abstract

The processes involved in the induction of facultative prepupal diapause in the parasitic wasp, Aphidius nigripes were investigated. Low temperatures and short daylengths experienced by the parasitoid were significant stimuli, as were the resulting interactions between these two factors. Sensitivity to diapause inducing conditions was greatest during embryonic and first-instar larval development. There was also evidence of several maternal effects. Females exposed to short daylengths and low temperatures during their adult life produced more diapausing offspring than those at long-day, high-temperature conditions, whereas conditions females experienced during their immature development had no significant effect. Furthermore, maternal age also influenced the incidence of diapause in the progeny. A higher proportion of parasitoids developing in small, first-instar aphid nymphs entered diapause than those developing in larger fourth-instar hosts. The multiplicity of factors, and the involvement of two generations, in diapause initiation of A. nigripes are considered as adaptations of a multivoltine species with a short developmental time, permitting the parasitoid to adequately assess seasonal changes in the environment.