Abstract
Ten species of Didineis Wesmael 1852 are recorded from Russia and adjacent territories. The new synonymy (valid name listed first) is established for Didineis bactriana Gussakovskij 1937 = D. ogloblini Gussakovskij 1937, D. clavimana Gussakovskij 1937 = D. turanica Gussakovskij 1937, and D. lunicornis (Fabricius 1798) = Didineis ruthenica Gussakovskij 1937. The number of valid species-group taxa in the genus Didineis is reduced to 25. The lectotypes are designated for four species: Didineis bactriana Gussakovskij 1937, D. botsharnikovi Gussakovskij 1937, D. clavimana Gussakovskij 1937, D. ruthenica Gussakovskij 1937. An original key to the species is provided.