Nebria (Falcinebria) reflexa Bates and its relatives are among the most diverse groups of the genus in Japan, but their diversity has not yet been fully elucidated. In this study, specimens from three regions that had not been covered previously—the Japanese Alps (central Honshu), Shikoku, and Kyushu—were examined. Descriptions of Nebria dracocephala sp. nov. (type locality: Honshu, Mount Ryûtô-san) and Nebria elephanta sp. nov. (type locality: Shikoku, Mount Tsurugi-san), a redescription of Nebria hikosana Habu (type locality: Kyushu, Mount Hiko-san), and new distribution records for N. niohozana Bates (Honshu, Mount Teraji-yama), N. furcata Sasakawa (Honshu, Mount Kurai-yama), Nebria dichotoma Sasakawa (Honshu, Hiraya-tôge Pass), and N. hikosana (Kyushu, Mount Seburi-san) are presented. Species identification was based on the morphology of the male genital endophallus, a membranous inner sac everted from the aedeagus. For N. dracocephala , N. elephanta , and N. hikosana , the endophallus morphology exhibited several notable features—marked intraspecific variation in the size and shape of the surface structures, such as lobes in N. dracocephala , and significant morphological modifications of the gonopore protrusion in N. elephanta and N. hikosana . These findings, together with information on related species from previous studies, provide new insights into the processes of differentiation and morphological evolution of N. reflexa and related species. A checklist and updated key to all Japanese species of Nebria (Falcinebria) are provided.
Kôji Sasakawa (Wed,) studied this question.