Field studies of the winter stoneflies (Plecoptera) in the upper part of the Asagaigawa River, in Niigata Prefec-ture, Japan, from December 2020 to March 2021, resulted in only two species, i.e. Apteroperla tikumana (Uéno, 1938) and Eocapnia nivalis (Uéno, 1929). The numbers of individuals of small sized species, i.e. A. tikumana accounted for 97.4 per cent of all, and the period of the emergence was January to March. Like E. nivalis in Asagaigawa River, if only one large sized species inhabit in the river, the number of individuals of that species was extremely smaller than the small sized species. Large sized species appeared about a month earlier than small sized species.
抄録全体を表示