Lasius is a genus of formicine ants. The type species for this genus is the black garden ant, Lasius niger. Other major members, which live in drier heathland, are the cornfield ant, L. neoniger, and L. alienus. Other species include the temporary social parasites of the L. mixtus group and the hyper-social parasite Lasius fuliginosus. Lasius flavus is also a commonly seen species, building grassy hillocks in undisturbed pasture. In the Alps, these mounds – always aligned east to catch the first rays of the rising sun – have been traditionally used by goatherds as natural compasses. Species in the subgenus Acanthomyops, in particular L. interjectus and L. claviger, are commonly known as citronella ants due to their citronella-like smell.

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