Key to Species

Worker Ants




Hymenoptera On-Line








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Japanese Name


Original Reference

Fabricius, J.C. (1804) Systema Piezatorum: 439 pp. Brunsvigae.


Small to medium sized formicine ants: length of workers around 2.5 - 5 mm. Body color pale yellow to jet black. Head subtriangular, with straight or somewhat concave posterior margin. Compound eyes well developed to relatively small. Workers with three ocelli. Mandibles each with 7 to 12 teeth. Maxillary and labial palpi respectively 6- and 4-segmented. Antennae with 12 segments; segments 3 to 7 together shorter than 8 to 12 together. Dorsum of mesosoma with two convex curves, representing the promesonotal and propodeal dorsa; propodeal section in profile at a lower level than promesonotal section. Propodeal spiracle approximately circular. Promesonotal dorsum with well-developed pubescence.


This genus is divided into five subgenera: Lasius, Cautolasius, Chthonolasius, Dendrolasius and Austrolasius. All but the last are present in Japan. The known world fauna comprises 80 species. Lasius is widely distributed in the Palaearctic and Nearctic regions, 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. Wilson (1955) first revised the Japanese Lasius species. Later studies include those of Yamauchi (1979) and Yamauchi & Hayashida (1968, 1970). These authors recognized 16 Japanese species in 4 subgenera. Ecological matters, including distributional data, habitat preferences and nuptial flight details were reported by Yamauchi (1980, 1981) and Yamauchi et al. (1986). The four Japanese subgenera are: (1) Subgenus Lasius [Japanese name: Ke-ari-azoku] (5 species). These ants are active on the ground. Some species are not easily separated using worker external morphology. (2) Subgenus Dendrolasius [Japanese name: Kusa-ari-azoku] (5 species). These are temporary social parasites of other Lasius species. They resemble each other, but the shape of the petiole provides characters for taxonomic separation. Females are relatively easily distinguished. Nests are constructed of carton and are usually found near tree roots. The ants smell like "Sansho", a Japanese pepper. They form long-term trunk trails and attend aphids on trees. (3) Subgenus Chthanolasius [Japanese name: Ameiro-ke-ari-azoku] (3 species). These are temporary social parasites of other Lasius species. Some species cannot be distinguished by external worker morphology alone. They are terrestrial. (4) Subgenus Cautolasius [Japanese name: Kiiro-ke-ari-azoku] (3 species). These are terrestrial, and engage in mutualism with root-feeding aphids. Their food is predominantly honey-dew obtained from aphid symbionts.


  • Wilson, E. O. (1955). A monographic revision of the ant genus Lasius. . Bull. Mus. Comp. Zool. Harv., 113, 1-201.
  • Yamauchi, K. (1979). Taxonomical and ecological studies on the ant genus Lasius in Japan (Hymenoptera: Formicidae). I. Taxonomy. Sci. Rep. Fac. Educ. Gifu Univ. (Nat. Sci.), 6, 147-181.
  • Yamauchi, K. & K. Hayashida (1968). Taxonomic studies on the genus Lasius in Hokkaido, with ethological and ecological notes (Formicidae, Hymenoptera). I.The subgenus Dendrolasius or jet black ants. J. Fac. Sci. Hokkaido Univ. Ser. VI, 16, 396-412.
  • Yamauchi & Hayashida , 1970
  • Yamauchi, K. (1980). Taxonomocal and ecological studies on the ant genus Lasius in Japan (Hymenoptera: Formicidae). II. Geographical distribution, habitat and nest site preferences and nest structure. . In Sci. Rep. Fac. Educ. Gifu Univ. (Nat. Sci.), .
  • Yamauchi, K. (1981). Taxonomy and ecology of the ant genus Lasius of Japan. . Nature and Insects, 16(3), 9-14.
  • Systema Piezatorum: 439 pp. Brunsvigae.
  • Yamauchi, K., K. Ito & N. Suzuki (1986). Observations on the nuptial flights of the ant genus Lasius. . Sci. Rep. Fac. Educ.Gifu Univ. (Nat. Sci.), 10, 1-11.


Original text by Mamoru Terayama and Katsusuke Yamauchi. English translation by Mamoru Terayama, edited by Robert W. Taylor.