Genus Dihelus Townes, 1970

Dihelus Townes, 1970: 170 . Type species: Dihelus rufipleuris Townes, 1970 . Original designation.

In Japan, two species, D. hylaevorus (Momoi, 1966) and D. niger Gupta & Gupta (1978) have been recorded. The latter species was described based on a single female (holotype) and a single male (allotype) and Gupta & Gupta (1978) noted that this species can be distinguished from D. hylaevorus by the surface sculpture of face, frons and propodeum and the coloration of T1–T4. Among them, the surface sculptures on face and propodeum are subjective and I could not recognize the differences between D. hylaevorus and D. niger . The surface sculpture of frons is somewhat objective, i.e., frons with ( D. hylaevorus) or without ( D. niger) rugae below anterior ocellus, while this character states gradually changed in size (Figs. 1C– F). Momoi (1966) described the coloration of metasomal tergites as “tergites 1 through 4, and an apicomedian large spot on tergite 8, white.” but paratypes and additional materials of D. hylaevorus indicate that this sentence may be “posterior margin of tergites 1 through 4...”. Gupta & Gupta (1978) referred this character states of D. hylaevorus without correction and thus the differences of T1–T4 between D. hylaevorus and D. niger are based on incorrect information. By the above reasons, I conclude that both species are same and D. niger is newly synonymized under D. hylaevorus (syn. nov.).