A taxonomic revision of the Palaearctic members of the subgenus Lasius s.str. (Hymenoptera, Formicidae).

A revision of the Palaearctic members of the ant subgenus Lasius s.str. is presented the fundamentals of which are application of Numeric Morphology-Based Alpha-Taxonomy (NUMOBAT), investigation of type specimens of 58 taxa, critical evaluation of original descriptions of further 22 taxa, and decision-making based on the GAGE species concept. Excluding nomina nuda and unavailable names, 80 taxa are considered which divide into 56 recognized good species (with 16 of these described here as new), 12 junior synonyms, 11 incertae sedis, and one name representing a F1 hybrid. Eighteen phenotypic characters – seven shape, eight seta and two pubescence characters as well as absolute size – were recorded numerically in 4900 worker individuals originating from 1722 nest or spot samples. The subdivision of the subgenera Lasius s.str. Ruzsky 1913, Cautolasius Wilson 1955, Dendrolasius Ruzsky 1913, Chthonolasius Ruzsky 1913 and Austrolasius Faber 1967 is clearly confirmed by morphological data with each of the 99 recognized Palaearctic species being unambiguously assignable to either subgenus. A key to the 56 Palaearctic species of Lasius s.str., subdivided into five geographic regions, is presented. All species are depicted as z-stack photos in two standard positions. The new species Lasius precursor sp. nov. is proposed as a model for transition from a largely monogynousmonodomous social type (exemplified by the sister species Lasius turcicus Santschi 1921) to a supercolonial type (exemplified by the closely related species Lasius neglectus Van Loon et al. 1990).