Abstract: 【Aim】 Different parasitoid species may parasitize a shared host in the same microhabitat. This study aims at understanding the intrinsic competition between parasitoids and providing data for evaluating the control effects of parasitoids in biological control. 【Methods】 We manipulated parasiting sequence and time interval of two solitary parasitoids, Meteorus pulchricornis (Wesmael) and Microplitis mediator (Haliday) that attacked larvae of the shared host  Mythimna separata (Walker). Survival of the two parasitoids in intrinsic competition and developmental parameters of M. pulchricornis were investigated and compared. 【Results】 M. pulchricornis offspring had higher survival rates than M. mediator in the competition under treatments with different combinations of parasitizing sequence and time intervals, reaching as high as 96.7% when parasitizing 24 h earlier. M. pulchricornis prolonged the larval duration when parasitizing hosts ahead of M. mediator compared to that when parasitizing alone (the control), but did not differ from the control when parasitizing after M. mediator. M. pulchricornisoffspring adults lived longer under each competition treatment than under the control. The adult size (measured by hind tibia length) of M. pulchricornisoffspring was significantly smaller under each competition treatment than under the control. 【Conclusion】 The results of this study suggest that M. pulchricornis outcompetes M. mediator in shared M. separata early instar larva hosts, but incurs negative impacts on its offspring development.

Key words: Meteorus pulchricornis, Microplotis mediator, interspecific competition, intrinsic competition, multiparasitism, life history traits