Definition of the Gonioctena subgeminata species group (Coleoptera, Chrysomelidae, Chrysomelinae), with descriptions of two new species from China and Vietnam

This paper defines and reviews the Gonioctena subgeminata species group of the subgenus Asiphytodecta Chen, 1935. The group contains the following five species, including two new to science: G. subgeminata (Chen, 1934), G. tonkinensis (Chen, 1934), G. oudai Cho & Borowiec, 2016, G. allardisp. nov., and G. mantilleriisp. nov. The species group restricted to China and Vietnam is characterized by a labrum without a tooth-like projection, elytral punctures arranged in discernible rows, and a setose aedeagus with a broad apical process. Gonioctena tonkinensis is newly reported as an ovoviviparous species. Habitus photographs, illustrations of diagnostic characters of each species, and a key to the species are provided.