Investigation of the diagnostic character of larvae of three species of tumbling flower beetles of Mordellistena parvula group (Mordellistena weisei, M. bicoloripilosa and M. brunneispinosa) was realized in the conditions of the Republic of Belarus. The morphological description of Mordellistena weisei larva was presented for the first time. The descriptions of M. bicoloripilosa and M. brunneispinosa larvae of the last age group were given. The comparative analysis of the morphological features of the larvae necessary for their exact diagnostics was carried out and showed that structure of mandibles and the carrying tine as well as the angle of their elation towards the top of the pygidium were the most typical diagnostic features which made it possible to distinguish the larvae of all species. Investigation results showed that the number of chaetae on larvae head on the sternite of pygidium could also be used for their identification. The larval host plant of the larvae of the studied species were pointed out