Holocynips hartmani (Hymenoptera: Cynipidae)
Bretz Mill area, Sierra National Forest, Fresno County, California
October 18, 2021

Multiple larval cells with pupae are in the exact center of this image, under the bark. Not much to see here without cutting through the bark -- barely even a bulge. This spot is near the base of a large canyon live oak (Quercus chrysolepis). The presence of wasp-sized exit holes nearby alerted me to the possibility that there may be larvae or pupae here.