Oak apple or oak gall is the common name for a large, round, vaguely apple-like gall commonly found on many species of oak. Oak apples range in size from 3/4 to 2 inches in diameter and are caused by chemicals injected by the larva of certain kinds of gall wasp in the family Cynipidae. The adult female wasp lays single eggs in developing leaf buds. The wasp larvae feed on the gall tissue resulting from their secretions. A) Cherry gall. B) Oak apple; it's gall-wasp (Teras terminalis or Cynips folli) shown above, enlarged. C) Blister gall (Spathegaster vesictrix) D) Spangle gall (Neuroterus lenticularis, shown above, enlarged. E) Marble galls (Cynips kollari, with one of the galls cut open, showing larva in its central chamber. F) Artichoki gall (Cynips gemmae, with wasp shown below, enlarged. G) Gall of Neuroterus fumipennis (to left of leaf) H) Currant gala (Spathegaster baccarat, on catkins, and above on under side of leaf, its insect below enlarged. I) Gall of Biorhiza aptera, on roots. No artist credited, undated.