Discovery of a soldier of the fossil genus Drymomyrmex (Hymenoptera, Formicidae, Formicinae) supports phragmotic behaviour in Late Eocene ants

A previously unknown soldier of the genus Drymomyrmex Wheeler, 1915 is described. This find confirms the dimorphism of the worker caste of this genus, represents the oldest known soldier among ants, and confirms the phragmotic morphology and behaviour of ants in the Late Eocene. The putative life style of the Drymomyrmex species and the taxonomic position of this genus are discussed. We propose to assign Drymomyrmex to the tribe Lasiini, in particular to the Cladomyrma Wheeler, 1920 group.