Oak gall

Description:

Oak gall is the common name for a large, round, vaguely apple-like gall commonly found on many species of oak. Galls are caused by chemicals injected by the larva of certain kinds of gall wasp in the family Cynipidae. Cynipini is the tribe partially responsible for the formation of galls known as oak apples on oak trees. Biorhiza pallida is a gall wasp species in the family Cynipidae.