Effects of host plant dioecy on leafminers and their parasitoids

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We aimed to clarify the effects of sexual difference of Eurya japonica (Theaceae) in vegetative growth pattern and foliar nutritional and secondaty substance contents on the ecology of a leafminer (Coptotonche japoniella, Tischeriidae, Lepidoptera) and its parasitoid community. However, the difference in the density of C. japoniella between male and female plants was yearly variable, so that we failed to attain the original aim. Instead, we revealed the following things:1. C. japoniella oviposited exclusively on leaves over aged one year and scarcely on current-year leaves. Old leaves had smaller amount of nitrogen contents, lower ratio of nitrogen to carbon and larger amount of epigarocatechin than current-year leaves. When females of C. japoniella were compelled to lay eggs on current-year leaves, hatched larvae were soon enclosed by transformed cells of the leaf tissue. Thus, the adaptive significance that females scarcely oviposit on current-year leaves would be to avoid leaves with hypersensitive response to mines rather than leaves with poor nutritional quality.2. Leaves with leafmining larvae killed experimentally began to abscise earlier and more rapidly than leaves with living larvae. This suggests that C. japoniella larvae inhibit the host plant from abscising mined leaves early.3. The parasitoid assemblage assariated with C. japoniella was composed of 12 species. Of them, one was koinobiont, and the others were idiobiont. Coexisting mechanisms in this assemblage seemed to be a quite high rate of hyperparasitism by idiobionts to the dominant koinobiont and wide host ranges of idiobionts.4. On the basis of investigation of specimens preserved in Osaka Prefecture University and Hokkaido University and those collected in the field, four species of Tischeriidae were found to be new to science. Furthermore, a new tischeriid species from Quercus sp. (Fagaceae) was collected in Jawa Island, Indonesia, where no tischeriids had been recorded.