Wheat sawfly \Wheat sawfly\ (a) A small European sawfly ({Cephus pygm[ae]us}) whose larva does great injury to wheat by boring in the stalks. (b) Any of several small American sawflies of the genus {Dolerus}, as {D. sericeus} and {D. arvensis}, whose larv[ae] injure the stems or heads of wheat. (c) {Pachynematus extensicornis}, whose larv[ae] feed chiefly on the blades of wheat; -- called also {grass sawfly}.