Effects of adult mass rearing on conspecific attack and superparasitism in the parasitoid Microplitis croceipes

Microplitis criceipes (Hymenoptera: Braconidae) is an endo-larval parasitoid of Heliothis/Helicoverpa spp. Recently, we found that M. croceipes females oviposit in conspecific adults (Takasu and Le, 2007). When reared in group in a cage, adult females often attacked other adults. The attacked adults contained the parasitoid egg at their abdominal cavity. About 30 % of the eggs laid hatched, the hatched larvae survived for 4-6 days but died without molting to second instar. When two naïve females reared in group for 4 days after emergence were placed on the plant leave infested with a host larva, they searched for hosts on the infested leaf, and on contacting, they attacked each other. About 30 % of them contained the parasitoid egg. However, when females were reared individually and then two of them were placed on the infested plant, they avoided to attack conspecifics. These results suggest that the presence of other conspecific adults causes the conspecific attack. Similarly, superparasitization behavior was different between individually rearing females and group rearing females. Females reared in group often superparasitized the hosts parasitized by conspecifics, while females reared individually often avoided superparasitism. Adult mass rearing increased the number of eggs stored in their calyx glands, which may increase ovipositional moviposition. This may cause frequent attacks to conspecifics or parasitized hosts.