A contribution to mayfly studies of Western Mongolia (Insecta, Ephemeroptera)

Abstract. Streams in the Mongolian Altai Mountains are mostly fed from glaciers and are extreme conditions for mayflies because of high elevation, low temperatures and low annual precipitation. Previous information about mayflies of Western Mongolia is scarce, but with this study a total of 38 species belonging to 26 genera and subgenera and 8 families of mayflies has been recorded in the Mongolian Altai region. Study material was entirely imagos and collected from 78 sites during expeditions led by the Mongolian Aquatic Insect Survey in 2008, 2009 and 2010. Raptobaetopus tenellus, Caenis luctuosa and Caenis rivulorum are recorded as new to the fauna of Mongolia, and there are new distribution records for Ameletus montanus, Baetis (Acentrella) lapponica, Baetis sibiricus, Baetis (Labiobaetis) attrebatinus, Centroptilum luteolum, Procloeon pennulatum, Ephemerella aurivillii, Serratella setigera, Ephemera sachalinensis, Ecdyonurus (Afronurus) abracadabrus, Cinygmula kurenzovi, Ecdyonurus (Afghanurus) vicinus and Epeorus (Belovius) pellucidus from the Mongolian Altai region. Baetis vernus and Ephemerella aurivillii are the most frequently encountered species in this region.