Lasius japonicus

Japanese Name

Tobiiro-ke-ari

Santschi, F. (1941) Quelques fourmis japonaises inŽdites. Mitteilungen der Schweizerischen Entomologischen Gesellschaft 18: 273-279.

Lasius emarginatus var. japonicus Santschi (Santschi, 1941) , Lasius niger (Linnaeus) (Wilson, 1955) , Lasius niger (Linnaeus) (Yamauchi & Hayashida, 1970) ,

Total length of workers around 2.5 - 3.5 mm. Body blackish brown, with the mesosoma often slightly lighter in color than the head and gaster. Scape length similar to head width. Scapes each with 5 to 25 erect hairs. Dorsal pronotal width in workers from mature colonies can exceed 0.70 mm. Petiole in profile with its dorsal margin bluntly angulate; anterior margin with a blunt angle.

The Japanese form has long been represented as Lasius niger, a species widely distributed in Eurasia. It was formally identified as L. japonicus by Seifert (1992).
Worker specimens from incipient colonies have fewer erect hairs on their scapes than others (fewer than 10), so they are difficult to separate from L. alienus workers. However, L. japonicus females are separated from those of L. alienus by the presence of erect hairs on the scapes and anterior tibiae. This species is most commonly found in grasslands and forests. It has a wide elevational range, from lowlands to mountainous areas in central Japan up to 2000 m above sea level. A distribution record from Okinawa Island (Naha City) might represent a population introduced by human commerce. Nests are found in the soil and rotting wood. The nuptial flights occur in July and August.

Hokkaido, Honshu, Shikoku, Kyushu, Yaku I., Tokara Is.; Korean Peninsula, Taiwan.