The plant tissue is remarkably altered even to the point of replication of chromosomes without cell division. Other less common gall producing insects are aphids, psyllids, and gall flies. Since most galls seem to do no permanent damage to their host plants, limited research has been done on the biology or control. This note is about galls formed on oak by gall wasps. Many gall wasps develop for 2 or 3 years in woody galls on the twigs of oaks.
Adults then emerge from the twig galls during the winter.
They lay eggs in the buds and die. When these eggs hatch, and new growth resumes on the oak, salivary secretions of the gall wasp grub act as powerful plant growth regulators and force the tree to form the gall. Gall wasp galls typically have an outer wall, a spongy fiber layer and a hard, seedlike structure inside of which the gall wasp grub develops. Although gall wasp grubs have chewing mouthparts, they do not seem to chew plant tissue. Evidently the gall secretes nutrients which the grubs lap up.