Trissolcus nigripedius Nakagawa and Telenomus gifuensis Ashmead (Hymenoptera: Scelionidae) are solitary egg parasitoids of Dolycoris baccarum L. (Hemiptera: Pentatomidae), a polyphagous seed-sucking bug of agricultural crops. Field examinations revealed that the two parasitoids are the most common species, but only a single species emerge from a host egg mass. To explain this observation we tested two hypotheses of interspecific host discrimination and asymmetry in competitive interaction between the two parasitoids. When provided with host eggs pre-parasitized by each other, both Tr. nigripedius and Te. gifuensis parasitized 94 and 100% of the host eggs without interspecific host discrimination, respectively. Interestingly, from the multiparasitized eggs irrespective of oviposition sequence, progeny of Te. gifuensis always survive better than Tr. nigripedius. Te. gifuensis is superior in immature competition probably due to shorter egg incubation period, hence progeny of Te. gifuensis become first instar faster than that of Tr. nigripedius. However, adult Tr. nigripedius is always superior competitor in possessing and guarding the host eggs even after oviposition against Te. gifuensis. Therefore, the asymmetry in competitive interaction between Tr. nigripedius and Te. gifuensis may explain the emergence of a single species from a host egg mass in the field in spite of no interspecific host discrimination.

숙주인 미국횐불나방 번데기의 기생여부와 밀도에 따른 무늬수중다리좀벌의 숙주식별행동을 조사하기 위하여 페트리 접시(1.59 cm)내에서 무늬수중다리좀벌의 숙주 번데기에 기생 시켰다. 무늬수중다리좀절의 중복산란률은 낮은 숙주 밀도에서 높게 나타났다. 무늬수중다리좀벌은 숙주에 산란여부를 촉각탐색과 산란관탐침에 의하여 식별할 수 있는 것으로 나타났다. 촉각탐색에 의해서 인식되는 물질은 기생벌이 숙주에 산란할 때 숙주표면에 표지되는 물질로써 일정시간 후에는 소멸되는 것으로 나타났다. 또한 무늬수중다리좀벌은 산란관 탐침으로 기생된 숙주의 내부변화를 식별하여 산란여부를 결정하는 것으로 조사되었다.