Zaika V.V. 2023. [The mayflies (Ephemeroptera) of the Us River basin in the Western Sayan mountains, Russia] // Euroasian Entomological Journal. Vol.22. No.2: 111–116 [in Russian, with English summary].
Tuvinian Institute for Exploration of Natural Resources, Russian Academy of Sciences, Siberian Branch, Internationalnaya Str. 117а, Kyzyl, Tyva Republic 667007 Russia. E-mail: odonta@mail.ru
doi 10.15298/euroasentj.22.02.11
ABSTRACT. The present work is based on the author’s collections data for the period of 2013–2021 years within the basin of the Us River. The Us River is a right tributary of the Yenisei River with the Aradanka and the Koyard tributaries belonging to the southern macroslope of the Western Sayan. The studies covered 53 km of its total length of 236 km, mainly in the summer months. 3232 larvae were collected where 34 older species are ready for metamorphosis (the present information allows us establish the breeding season start of a particular species) as well as 11 imago males and 10 females belonging to 31 species. The most common and numerous species found within all rivers sections were Baetis pseudothermicus Kluge, 1983 and Rhithrogena (Cinygmula) cava Ulmer, 1927. The species Ameletus altaicus Kluge, 2007, Baetis bicaudatus Dodds, 1923, Epeorus (Belovius) pellucidus Brodsky, 1930, Neoleptophlebia japonica Matsumura, 1931 are recorded as densely spreaded. A comparison of the species composition of the Nizhnyaya Buiba River and the Us River according to the Sorensen-Chekanovsky index showed that it is equal to 0,77. The similarity of the species composition of the Us River with the Aradanka and the Koyard rivers is less — only 0,59 and 0,55 respectively. The similarity index of species diversity of the Us River with the rivers of the northern macroslope of the Western Sayan is 0,65, and with the Upper Yenisei is 0,60. Species Ephemerella atagosana Imanishi, 1937 are firstly indicated for Altai-Sayan and Southern Siberia as a whole, and the species Seratella setigera (Bajkova, 1967) are indicated for the first time for the watercourses of the entire Western Sayan.
KEY WORDS: Ephemeroptera, fauna, Us River basin, Western Sayan.