Galls, Diseases, and Pests - Coyote Brush Bud Gall Midge
Rhopalomyia californica
The Coyote Brush Bud Gall Midge is a small flying insect. The females only live through about one day outside of the gall, which includes emerging from the gall, mating, and laying eggs. The eggs are laid in the buds on the ends of branches, and this causes a gall to develop. The life cycle can take place throughout the year, and often galls can be found with partially protruding exuviae (the remains of an exoskeleton) left by emerging pupae.
You can see some of the spent exuviae on this gall--the little white sheaths sticking out from the surface. There is also a midge on the leaf to the upper left.
This is a little better view of the midge as well as the exuviae.