New gall wasp species attacking chestnut trees: Dryocosmus zhuili n. sp. (Hymenoptera: Cynipidae) on Castanea henryi from southeastern China.

A new gall wasp species, Dryocosmus zhuili Liu et Zhu, is herein described from the southeastern Fujian province of China. The new species induces galls on trees of Henry's chestnut, Castanea henryi, which is also a native host for the notorious Oriental chestnut gall wasp (OCGW, Dryocosmus kuriphilus Yasumatsu). D. zhuili overlaps with OCGW in emergence time and induces galls morphologically similar to that of OCGW on similar plant parts. In a previous study, we reported considerable divergence between mtDNA CO1 (mitochondrial DNA Cytochrome c oxidase subunit I) sequences of these wasps and the true OCGW wasps and suggested the existence of a cryptic species. Herein, we confirm the identity of the new species based on morphological and biological differences and provide a formal description. Although the new species is relatively easily separated from OCGW on basis of morphology, field identification involving the two species can still be problematic because of their small body size, highly similar gall morphology, and other life history traits. We further discussed the potential of the new species to be a pest for the chestnut industry and the consequences of accidental introduction of this species into nonnative areas, especially with regard to the bisexual reproduction mode of the new species in contrast to the parthenogenetic reproduction mode of OCGW.