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I think that Cthirion's suggestion of Caenolyda reticulata is likely to be correct, though the picture on the Russian site hardly does it justice.
There is a relatively new book that includes the Pamphiliidae:
Sawflies (Hymenoptera, Symphyta), Volume 1. A Review of the Suborder, the Western Palaearctic Taxa of Xyeloidea and Pamphilioidea. Edited by Matti Viitasaari 1999 Tremex Press.
This almost certainly has the answer, but unfortunately I can't afford to buy it! :(