Ovipositional Traits of the Chestnut Gall Wasp, Dryocosmus kuriphilus (Hymenoptera : Cynipidae)

This study examined whether differences in bud size affected the oviposition behavior of the chestnut gall wasp, Dryocosmus kuriphilus. The frequency of multiple oviposition by the same or other conspecific adults on a single bud was examined. The mean dry weight was significantly larger in buds with eggs laid than in ones with no eggs, in buds with one or more oviposition scars than in ones with no scars, and in buds with multiple oviposition scars than in ones with a single oviposition scar. Thus, D. kuriphilus adults preferred large buds for oviposition. The proportion of buds with multiple oviposition scars increased significantly with an increasing proportion of buds with eggs laid. The regression coefficient of the mean number of eggs laid per bud on the number of oviposition scars was significantly larger than 1.0. These results suggest that D. kuriphilus adults laid eggs repeatedly in a larger bud under high densities. The ovipositional site selection for larger buds in D. kuriphilus may be adaptive when migration from one ovipositional site to another is risky, and when larval performance decreases due to overcrowding in a bud by multiple oviposition.