The wooly bud gall midge (Rhopalomyia medusirrasa) reminds me of dodder (Cuscuta sp.) – a plant and an insect that in their own ways are both odd, fascinating and strange looking.
The wooly bud gall midge induces globular, leafy, pubescent galls on the buds of tall sagebrush (Artemesia tridentata). The large, polythalamous (many chambered) galls are actually composed of numerous leaflike structures covered in long, forked white hairs. There is another gall midge that also infects tall sagebrush buds (Rhopalomyia medusa) and causes the formation of similar galls, only R. medusa galls lack the white hairs.
During the summer wooly bud gall midges lay their eggs on the buds of tall sagebrush. The galls begin to form in October when the larvae hatch and begin to feed, are dormant over the winter and reach their full size in the spring when each gall can contain up to four midge larvae. In April or May adults emerge from the galls and begin the cycle again.
I do not know if the galls harm tall sagebrush, although a heavy infestation could not be beneficial to the shrub.
These wooly bud midge galls were growing on tall sagebrush along Ash Creek in Lassen County CA.