(Figs 55, 67)
Idaea imbecilla: Beljaev & Mironov 2019: 277 (Sakhalin).
Material examined. 1 ♂, Yuzhno-Sakhalinsk, STAZR, 04.VII.2007; 1 ♂, 1 ♀, Yasnomorskoe, 18, 20.VII.2019.
Distribution. Russia (S RFE: S Sakhalin, S Kurils—Kunashir), Japan (Hokkaido, Honshu, Shikoku, Kyushu, Tsushima, Yakushima), South Korea.
Remarks. The finding of I. imbecilla in Sakhalin significantly expands its distribution range to the northeast.