Survival rates of the first and second offspring of Echthrodelphax fairchildii Perkins (Hymenoptera: Dryinidae) under self and conspecific superparasitism: The effects of body size of ovipositing females

The effects of ovipositing female body size on the survival of the first and second offspring under self and conspecific superparasitism have not been determined. Here, we report the importance of the body size of ovipositing females for three intervals (0, 1, and 24 h) between first and second ovipositions using a semi-solitary ectoparasitoid, Echthrodelphax fairchildii, and fourth-instar nymphs of its host, the planthopper Laodelphax striatellus. We addressed the case in which the first and second parasitoid eggs were laid on different sides of the same host. The second ovipositing female killed the previous offspring using the sting, but when the oviposition intervals were 0 and 1 h, the elimination was unprofitable because both offspring often emerged under non-probing superparasitism. The survival rate of the second offspring decreased with increasing oviposition intervals under non-probing superparasitism, whereas that of the first offspring was independent of oviposition intervals. Under non-probing superparasitism, the survival rates of the first and second offspring were higher under conspecific superparasitism than under self superparasitism, especially when the first and/or second ovipositing females were small. Large mothers ensured high survival rates of their offspring under non-probing superparasitism, except the survival rate of the second offspring under conspecific superparasitism, which was negatively associated with the first female's size. Thus, the first offspring from small mothers were likely to lose the competition to the second offspring. Under probing superparasitism, the second offspring survival rate was positively associated with the mother's size, suggesting that offspring, not ovipositing females, release agents affecting the mother-size effect.