Carabus japonicus

Carabus japonicus is a ground beetle endemic to Japan. It inhabits the southwestern Japanese forests and is most frequently observed between May and September, with peak observations occurring mid-August. C. japonicus is a univoltine species, meaning it has one brood of offspring per year. Its larvae prey exclusively on earthworms. At lower altitudes, the reproductive cycle has been shown to coincide with the abundance of earthworms. This demonstrates the synchronization between the life cycles of the two species. The males tend to be slightly smaller than the females with both sexes having median body sizes of 24 mm and 26 mm, respectively. However, there is a large variation in intraspecific body size due to factors other than sex. These factors include parent size, food availability, and habitat temperature.