Rhopalomyia floccosa, the sagebrush woolly stem gall midge, is a species of gall midges, insects in the family Cecidomyiidae. It induces galls on the host "Artemisia californica", California sagebrush. 
Galls and biology.
An individual gall measures in diameter. Coalescing galls may be in length. The midge produce white, wooly, monothalamous bud galls.