Distribution of Trephionus spp. in central Honshu based on specimens with unambiguous identities. ◆ T. nikkoensis ★ T. mikii ■ T. kinoshitai ▼ T. cylindriphallus sp. n. ▲ T. niumontanus sp. n. ● T. babai ○ T. subcavicola △ T. shibataianus ◇ T. inexpectatus sp. n. ☆ T. abiba sp. n. □ T. bifidilobatus sp. n. The type localities of T. nikkoensis, T. mikii, and T. subcavicola, which were not examined in this study, are shown, although the validities of their species statuses remain to be examined.