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 mitsukurii Ashmead, 1904 syn. nov. Moreover, we examined the type specimens of other species previously suggested to be synonymous with D. mitsukurii. This showed that Neuroterus vonkuenburgi Dettmer, 1934 syn. nov. (and N. vonkuenburgi wakayamensis Monzen, 1954 syn. nov.) is the asexual generation of C. japonicus and that Neuroterus bonihenrici Dettmer, 1934 syn. nov. is the sexual generation. Judging from the original descriptions, Andricus asakawae Shinji, 1943 syn. nov., Andricus kanagawae Shinji, 1943 syn. nov., Andricus asakawae Shinji, 1944 syn. nov., Andricus kanagawae Shinji, 1944 syn. nov., and Neoneuroterus kashiyamai Monzen, 1954 syn. 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.