This study clarifies taxonomic problems in Pterostichus macrogenys Bates, 1883, a Japanese endemic flightless carabid beetle. Specifically, to address the lack of examination of the male genitalia of the type specimens and a potential risk regarding nomenclatural stability, the syntype male is designated as the lectotype and its genitalia (including the sufficiently inflated endophallus) are examined. The results confirm that the species previously treated as P. macrogenys is indeed P. macrogenys. Additionally, a male specimen from Mt. Amagisan on the Izu Peninsula is reported as the southernmost collection record of this species.

Fragmenta entomologica, Vol. 56 No. 2 (2024)