In vivo and in vitro developmental profiling of Asobara japonica, a larval endoparasitoid of drosophilid flies

The relationship between host and parasitoid has been examined in terms of either the effects of infestation on host growth and development, or the growth and development of parasitoid larvae in response to the physiological and nutritional status of their hosts. Although a wide range of host–parasitoid interactions has been studied, detailed developmental profiles of parasitoid larvae and environmental effects on them have remained unclear in many cases because the parasitoid larvae are relatively inaccessible inside their hosts. Here, we used Drosophila melanogaster Meigen (Diptera: Drosophilidae) and Asobara japonica Belokobylskij (Hymenoptera: Braconidae) as a model system to describe developmental profiles of hosts and endoparasitoid wasps, and investigated environmental factors that affect the developmental profiles in in vivo and in vitro culture experiments. As a result, we successfully identified six morphologically distinct developmental stages (I–VI) of pre-adult A. japonica. The current approach based on qualitative and quantitative assessment of wasp morphology may be an effective approach for estimating the instar number of endoparasitoids lacking sclerotized structures in general. The finding that the development of A. japonica from stage III to stage IV is constrained by host developmental stage regardless of the environmental conditions in this study suggests that developmental mismatch may be an important factor in the evolution of host selection in endoparasitoid wasps.