Sphaeroteras trimaculosum (Hymenoptera: Cynipidae)   (Synonym: Atrusca trimaculosa)
Woollybear Gall Wasp
Cosumnes River Preserve, San Joaquin County, California
October 19, 2007

This is a Sphaeroteras trimaculosum gall with Andricus fullawayi galls on either side of it. You can see the difference in hairs on these galls -- the hairs on the Sphaeroteras trimaculosum gall are shorter, stiffer, and more rusty brown than the hairs on the other galls. On Quercus lobata (Valley Oak).