Spatial density-independent parasitism of the inquiline, Diomorus aiolomorphi (Hymenoptera: Torymidae), on the bamboo gall maker, Aiolomorphus rhopaloides (Hymenoptera: Eurytomidae)

Abstract

Diomorus aiolomorphi Kamijo (Hymenoptera: Torymidae) is an inquiline on bamboo galls formed by the bamboo gall maker Aiolomorphus rhopaloides Walker (Hymenoptera: Eurytomidae). I examined (1) the spatial and vertical distribution of galls and galls from which D. aiolomorphi emerged, and (2) the spatial density-dependent parasitism of D. aiolomorphi in a stand of Phyllostachys heterocycla. The percentages of galls from which D. aiolomorphi emerged tended to be higher than those from which A. rhopaloides emerged and ranged from 21.5% to 45.6%. Bamboo galls and galls from which D. aiolomorphi emerged were distributed contagiously on bamboo culms and branches. The attack of D. aiolomorphi was not dependent on gall density on culms and branches. D. aiolomorphi is synovigenic; females have no eggs in their ovaries when they emerge but develop eggs continuously as adults age. Thus, D. aiolomorphi females cannot lay eggs on freshly initiated galls aggregatively and successively, suggesting that D. aiolomorphi attacks regardless of gall density.