Colobopsis explodens sp. n., model species for studies on “exploding ants” (Hymenoptera, Formicidae), with biological notes and first illustrations of males of the Colobopsis cylindrica group

Abstract

A taxonomic description of all castes of <i>Colobopsis explodens</i> Laciny & Zettel, <b>sp. n.</b> from Borneo, Thailand, and Malaysia is provided, which serves as a model species for biological studies on "exploding ants" in Southeast Asia. The new species is a member of the <i>Colobopsis cylindrica</i> (COCY) group and falls into a species complex that has been repeatedly summarized under the name <i>Colobopsis saundersi</i> (Emery, 1889) (formerly <i>Camponotus saundersi</i>). The COCY species group is known under its vernacular name "exploding ants" for a unique behaviour: during territorial combat, workers of some species sacrifice themselves by rupturing their gaster and releasing sticky and irritant contents of their hypertrophied mandibular gland reservoirs to kill or repel rivals. This study includes first illustrations and morphometric characterizations of males of the COCY group: <i>Colobopsis explodens</i> Laciny & Zettel, <b>sp. n.</b> and <i>Colobopsis badia</i> (Smith, 1857). Characters of male genitalia and external morphology are compared with other selected taxa of Camponotini. Preliminary notes on the biology of <i>C. explodens</i> Laciny & Zettel, <b>sp. n.</b> are provided. To fix the species identity of the closely related <i>C. badia</i>, a lectotype from Singapore is designated. The following taxonomic changes within the <i>C. saundersi</i> complex are proposed: <i>Colobopsis solenobia</i> (Menozzi, 1926), <b>syn. n.</b> and <i>Colobopsis trieterica</i> (Menozzi, 1926), <b>syn. n.</b> are synonymized with <i>Colobopsis corallina</i> Roger, 1863, a common endemic species of the Philippines. <i>Colobopsis saginata</i> Stitz, 1925, <b>stat. n</b>., hitherto a subspecies of <i>C. badia</i>, is raised to species level.