Lasius

Lasius is a genus of ants, family Formicidae, subfamily Formicinae, comprising 149 species, commonly called garden ants, with the type species Lasius niger, the black garden ant; species in the subgenus Acanthomyops are called citronella ants for their distinctive odor. The genus is widespread globally, with a fossil record extending from the Eocene period, roughly 46 million years ago, to the present. Workers are monomorphic, measuring 2 to 3 millimeters and ranging from yellow to dark brown, distinguished from carpenter ants by a notch in the dorsal thorax; many species, called moisture ants, nest in rotting wood and moist locations, some show social parasitism using chemical signals to invade colonies, and Lasius flavus builds distinctive grassy mounds that alpine populations traditionally used as natural compasses.