Qualitative and quantitative samplings of adult winter stoneflies were conducted in May and/or June 2014, 2015 and 2018 in three snowy valleys at the eastern face of Mt. Tanigawa, northern Gunma Prefecture, central Japan, to reveal faunal composition of stoneflies in snowy valleys which remain until early to late summer. Seven species of winter stoneflies belonging to five genera and three families were collected. Population density of the winter stoneflies ranged from 3.8 to 87.5 individuals per square meter. At least in two valleys, Ichinokurasawa and Yuunosawa, the populations were largely dominated by Apteroperla sp. A8 (Capniidae). Most of the female capniid stoneflies found in May and June had mature eggs. Influence of floods on population density of stoneflies was discussed.
