Callirhytis flora (Hymenoptera: Cynipidae)
Live Oak Petiole Gall Wasp
Copperopolis, Calaveras County, California
November 6, 2007

Wasps develop in the acorn and abort the acorn's growth. An exit hole is visible (likely from a parasitoid/inquiline). From Quercus wislizenii (interior live oak).