Abstract:  【Aim】 The “dome-shaped” hypothesis suggests that medium aged host larvae are higher in quality than the two ends of host instar for fitness of solitary braconid and ichneomonid parasitoids attacking lepidopteran larvae. The hypothesis receives support from numerous studies, but most of these empirical studies tested host larval instars and gave little focus on reproductive performances of offspring parasitoids, leading to inaccurate and incomplete description of parasitoid fitness as a function of host age at parasitism. This study aims to test this hypothesis by focusing on host larval age in days. 【Methods】 In this study, we exposed Spodoptera litura larvae at different days of age from late 1st instar to early final instar to Meteorus pulchricornis for parasitism, and examined the parasitizing, developmental and reproductive parameters of the parasitoid. 【Results】 The linear regression results showed that M. pulchricornis female wasps had higher parasitism rate on medium aged hosts than on younger and older hosts at oviposition. The egg-to-adult survival, adult body size and fecundity (number of eggs laid) of the parasitoid were greater in medium aged hosts as compared to those in younger and older hosts. 【Conclusion】 Our study provides the solid support to the “dome-shaped” hypothesis.

Key words:  Meteorus pulchricornis, Spodoptera litura, developmental strategy, host age, host quality, koinobiont, reproduction, body size