It is an early stage of a Bibionidae. Although I cannot rule out Pleciidae entirely. I don't know if Penthetria in an earlier stage also has these short thoracic/abdominal tubercles, but probably not. When fully mature, the larva of Penthetria looks a bit like Phalacrocera, but when you take a closer look there are some major differences. Penthetria is unlike Bibionidae more or less restricted to forestbrooks. So I assume that it is not a Penthetria.
Does someone has a scan of Nartshuk E.P. 2003. Key to families of Diptera (Insecta) of the fauna of Russian and adjacent countries. Proceedings of the Zoological Institute Vol. 294: 1-252 for me?
