Breaking the monotypy: Insights into an enigmatic ant genus with the discovery of Ishakidris hastifera sp. nov. in Peninsular Malaysia

Ishakidris Bolton, 1984 is a monotypic ant genus, previously known only from a solitary specimen collected in Sarawak, Borneo. Unusual morphology of the genus has kept scientists intrigued since its description. Here we report on the discovery of Ishakidris hastifera sp. nov. from Peninsular Malaysia that provides important new insights into the taxonomy of this enigmatic genus and sheds light on its previously unknown diversity and distribution. We present a detailed account of the worker’s diagnostic features, aided by a micro-CT–based 3D model of the holotype, together with a cybertype dataset for the new species and an identification key for the genus. In addition, a 3D model of non-type material is made available for the already established species, Ishakidris ascitaspis Bolton 1984, using additional workers newly collected in Sabah, Borneo. Our analysis of both species’ internal structures, enabled by the 3D models, revealed a shelf-like invagination of the propodeum into the mesosomal cavity – an unprecedented character in ants. Using the morphological data, we discuss the support for the current systematic placement of the genus in Myrmicinae subfamily, or alternative hypothesis for Agroecomyrmecinae, that calls for molecular data to be yet tested.