Propodeal spiracle approximately circular. Promesonotal dorsum with well-developed pubescence. The known world fauna comprises 40 species. Lasius is widely distributed in the Holarctic region, occurring commonly in habitats ranging from bare areas to forests. Many species attend aphids and coccids in strongly mutualistic associations.
Some species form distinct foraging trails.
These authors recognized 16 Japanese species in 4 subgenera. These ants are active on the ground. Some species are not easily separated using worker external morphology. These are temporary social parasites of other Lasius species. They resemble each other, but the shape of petiole provides characters for taxonomic separation.