Nicagus japonicus Nagel

Nicagus japonicus Nagel (Fig. 4 c)

Nicagus japonicus Nagel, 1928: 260.

Diagnosis. This species differs from both Nearctic species in possessing an evenly rounded lateral margin of the pronotum (not angulate as in the Nearctic species) with stronger, tooth­like crenulations. In addition, N. japonicus has the anterior margin of the clypeus subtriangular and not rounded, and the claws are relatively short and subequal in length to tarsomeres 3–4 together. Males have a bidentate protibial apex (Fig. 4 c), rather than an apex with a single large tooth, and the inner margin of the metatibia is convex in dorsal view. Also in males, the first antennal club segment is not simply cylindrical, and instead is bulbous medially and narrows abruptly to the apex. The median lobe of the male genitalia lacks the ventral concavity present in the Nearctic species and the parameres are less strongly curved, appearing almost straight in dorsal view.

Distribution. Fifteen specimens examined (11 male, 4 female).

JAPAN: AKITA: Mose­Hachimantai (CMNC). HOKKAIDO: Mena River north of Hakodate (FMNH). NIIGATA: Nakauonuma: Kawanishi (MJPC). A distributional map in Tabana & Okuda (1992) includes localities on the islands of Hokkaido and Honshu in the following prefectures: AKITA, FUKUI, FUKUSHIMA, GIFU, HOKKAIDO, HYOGO, KYOTO, MIE, NARA, NIIGATA, TOYAMA.