The genus is well defined and was reviewed by Fjellberg (1986) and Fjellberg & Bernard (2009). In the course of our study of neustonic fauna two species were collected. One of them, supposedly a new species, belonged to ' bidenticulata ' group and differed from the widely distributed arctic species A. bidenticulata by longer claws. To clarify the independence of the Buryatian form we have studied other populations of A. bidenticulata from Russian Arctic and Siberian mountains.