Systematics of the ant genus Proceratium Roger (Hymenoptera, Formicidae, Proceratiinae) in China – with descriptions of three new species based on micro-CT enhanced next-generation-morphology

Abstract

The genusProceratiumRoger, 1863 contains cryptic, subterranean ants that are seldom sampled and rare in natural history collections. Furthermore, mostProceratiumspecimens are extremely hairy and, due to their enlarged and curved gaster, often mounted suboptimally. As a consequence, the poorly observable physical characteristics of the material and its scarcity result in a rather challenging alpha taxonomy of this group. In this study, the taxonomy of the ChineseProceratiumfauna is reviewed and updated by combining examinations of traditional light microscopy with x-ray microtomography (micro-CT). Based on micro-CT scans of seven out of eight species, virtual 3D surface models were generated that permit in-depth comparative analyses of specimen morphology in order to overcome the difficulties to examine physical material ofProceratium. Eight Chinese species are recognized, of which three are newly described:ProceratiumbruelheideiStaab, Xu & Hita Garcia,sp. n.andP.kepingmaisp. n.belong to theP.itoiclade and have been collected in the subtropical forests of southeast China, whereasP.shoheisp. n.belongs to theP.stictumclade and it is only known from a tropical forest of Yunnan Province.ProceratiumnujiangenseXu, 2006syn. n.is proposed as a junior synonym ofP.zhaoiXu, 2000. These taxonomic acts raise the number of known ChineseProceratiumspecies to eight. In order to integrate the new species into the existing taxonomic system and to facilitate identifications, an illustrated key to the worker caste of all Chinese species is provided, supplemented by species accounts with high-resolution montage images and still images of volume renderings of 3D models based on micro-CT. Moreover, cybertype datasets are provided for the new species, as well as digital datasets for the remaining species that include the raw micro-CT scan data, 3D surface models, 3D rotation videos, and all light photography and micro-CT still images. These datasets are available online (Dryad, Staab et al. 2018, http://dx.doi.org/10.5061/dryad.h6j0g4p).