Lasius platythorax n. sp. a Widespread Sibling Species of Lasius niger (Hymenoptera: Formicidae)
The antsknownas "Lasius niger" consist of 2 clearly different biospecies in Central Europe and S Sweden. Lasius niger (Linnaeus 1 758) is redescribed on the basis of 132 nest samples; a female specimen from S Sweden is determined as neotype. Lasius platy thorax n. sp. is described as new on the basis of 134 nest samples. The morphological differences of Lasius niger and platythorax n. sp. are very distinct throughout the studied territories. Using character combinations of weighted pro notal and gular hair length and clypeal pubescence distance in the female and of relative mesosoma height and clypeal pubescence distance in the female it was possible to determine each individual in the whole material. L. niger and platythorax are both widely distributed, but there is a very strong habitat segregation in Central Europe. L. niger prefers moderately xerothermous cultural habitats and has a strong synanthropic trend. L. platythorax is characteristic for different kinds of woodland, bogs and fens and avoids urban habitats. At the rare spots of syntopic occurrence, clear differences in the mode of nest construction are observed: L. niger is preferentially a digger and above-ground constructor with mineralic soil particles, while L. platy thorax is more an excavator of various preformed organic spaces. L. niger may reach much higher nest densities than platy thorax and prefers habitats with lower soil moisture. There is no evidence that the Palaearctic taxa alienoniger, grandis, transylvanica, favescens, emeryi nitidus, nigrescens, pilicornis, minimus, sakagamii, hayashi japonicus and coloratus could be synonyms of platythorax n. sp.