The Heterogonic Life Cycles of Oak Gall Wasps Need to Be Closed: A Lesson From Two Species of Dryophanta (Hymenoptera: Cynipidae: Cynipini)

Abstract

Abstract In heterogonic gall wasps, the gall structure, phenology, and adult morphology differ between the asexual and sexual generations, even within the same species. Dryophanta japonica Ashmead and Dryophanta mitsukurii Ashmead were described in 1904, but their heterogonic life cycles were uncertain. To match their asexual and sexual generations, we compared the type specimens of both species with specimens of gall wasps reared to demonstrate heterogonic life cycles. This revealed that these two species are the respective asexual and sexual generations of a single heterogonic species. Based on the morphological characteristics, we transferred D. japonica to Cerroneuroterus Melika and Pujade-Villar as Cerroneuroterus japonicus (Ashmead, 1904) comb. nov. and treated the sexual generation as a junior synonym: Dryophanta mitsukuriiAshmead, 1904syn. nov. Moreover, we examined the type specimens of other species previously suggested to be synonymous with D. mitsukurii. This showed that Neuroterus vonkuenburgiDettmer, 1934syn. nov. (and N. vonkuenburgi wakayamensisMonzen, 1954syn. nov.) is the asexual generation of C. japonicus and that Neuroterus bonihenriciDettmer, 1934syn. nov. is the sexual generation. Judging from the original descriptions, Andricus asakawaeShinji, 1943syn. nov., Andricus kanagawaeShinji, 1943syn. nov., Andricus asakawaeShinji, 1944syn. nov., Andricus kanagawaeShinji, 1944syn. nov., and Neoneuroterus kashiyamaiMonzen, 1954syn. nov. were also regarded as the sexual generation of C. japonicus. Finally, we discussed how matching asexual and sexual generations in heterogonic gall wasps not only avoids taxonomic confusion but also contributes to progress in gall wasp biology.