We have studied the fauna of several Diptera families caught with beer traps. In this paper, 36 species from 12 Diptera families are reported: four species of Anisopodidae, one species of Bibionidae, one species of Clusiidae, two species of Dryomyzidae, 11 species of Lauxaniidae, five species of Limoniidae, one species of Megamerinidae, three species of Pallopteridae, one species of Piophilidae, one species of Platystomatidae, four species of Sciomyzidae, and two species of Ulidiidae. From these species, three are new for Russia (Calliopum splendidum, Homoneura biumbrata, Sapromyza schnabli, all Lauxaniidae), two new for European Russia (Sylvicola fuscatoides (Anisopodidae), Myennis sibirica (Ulidiidae)). For the Republic of Mordovia and the Mordovia State Nature Reserve, the families Anisopodidae, Clusiidae, Megamerinidae, Pallopteridae, Piophilidae, Platystomatidae, Ulidiidae, and all Lauxaniidae species published in this list are recorded for the first time. Two species from the family Limoniidae (Achyrolimonia neonebulosa and Discobola parvispinula) and three species from the family Sciomyzidae (Euthycera chaerophylli, Tetanocera ferruginea and T. freyi) are recorded for the first time for the territory of the Mordovia State Nature Reserve. Beer traps can be recommended as one of the successful methods for future surveys of Diptera in the area of interest.