Various oak species, especially pin, scrub, black, blackjack, and water oak.
The current galls are two to three years old and they derive their name from the numerous
cone-shaped horns which protrude through the galls' surface. Each horn houses a single
larva which will mature during spring into a parthenogenetic (meaning eggs do not need to be fertilized)
female. These females lay eggs on veins on the underside of newly formed oak leaves.
Once the eggs hatch, elongated leaf vein galls form which enclose the larvae. In the
mid-to-late summer, males and females emerge from the leaf galls, mate, and the females
lay eggs on twigs. When these eggs hatch, new horned oak galls form around the larvae.
After two to three years, the process starts all over again.
Please contact your local county extension office for current information.