Four new species of Leptanillinae (Hymenoptera: Formicidae) from northern Vietnam described with phylogenomics and micro-computed tomography

The enigmatic ants of the subfamily Leptanillinae (Hymenoptera: Formicidae) are rarely collected, being minute and largely subterranean in biology. Vietnam is one of only two countries from which all three leptanilline genera are recorded; yet, only one described species has so far been reported from the country (Opamyrma hungvuong Yamane et al., 2008). Here, we describe four new species of Leptanillinae from Vietnam: Protanilla rong sp. nov., Leptanilla belantanoides sp. nov., Leptanilla sapa Yamada sp. nov., and Leptanilla phthirigyna sp. nov. We present the first detailed description of the larva of Protanilla (Protanilla rong); and of the male and gyne of Protanilla gengma Xu, 2012, the first time these forms have been described for the Protanilla bicolor species-group. We include volumetric reconstructions of the worker caste in Leptanilla charonea Barandica et al., 1994, Leptanilla belantanoides, Leptanilla sapa, Protanilla rong, and the gyne of the latter two species, derived from micro-computed tomography (μ-CT); and present the results of maximum-likelihood and Bayesian phylogenomic inference with the most comprehensive sampling of the Leptanillinae yet published. We also associate the male and worker of Leptanilla belantanoides by phylogenomics, providing the first such linkage for any species of the Leptanilla thai species-group; and resolve the phylogenetic placement of the bizarre Protanilla izanagi Terayama, 2013. Volumetric reconstruction of frontoclypeal skeletomusculature in Leptanilla via μ-CT elucidates anterior cranial anatomy in that genus.