Callirhytis apicalis (Hymenoptera: Cynipidae)   (Synonym: Andricus apicalis)
Knowland Park, Oakland, Alameda County, California
February 26, 2011

Root galls at the base of Quercus agrifolia (coast live oak) trunk. Most of the galls visible in this photo are old and have exit holes where the wasps emerged during previous years. The red arrow is pointing to one gall from this season (wasp still inside).