[Eliason and Potter provide a thorough description of the phenology, morphology, and parasitoid and inquiline communities of both the agamic generation, forming large horned stem galls, and the sexual generation, forming inconspicuous galls on leaf veins. Pictures are included of both galls.]

Callirhytis quercuscornigera (Osten Sacken)

Diagnosis. Wasps from the tiny, blister-like leaf galls were previously known as the alternate generation (Felt 1940). These galls resemble the leaf galls induced by C. pomiformis (McCracken & Egbert 1922), but leaf galls induced by C. quercuscornigera occur on the midveins, large lateral veins, and infrequently on petioles and tiny lateral veins (Eliason & Potter 2000).

Distribution. Canada: Ontario; USA: New York, Massachusetts, Connecticut, District of Columbia, Maryland, west to Illinois, Indiana, Montana, Iowa, Arkansas, Tennessee, Colorado, Texas, south to Virginia, North Carolina (Q. hemisphaerica and Q. falcata), Alabama, Georgia. New for Florida (Q. hemisphaerica. Trees in May 1995 were heavily infested; entire branches were killed by the galls and inducers).

Sexual leaf galls were observed on Q. palustris and Q. phellos.

Biology. The biology of both generations of C. quercuscornigera was recently described in Lexington, Kentucky (Eliason & Potter 2000).

Asexual females exit ∼33-month-old stem galls and oviposit into swelling buds (Eliason & Potter 2000). Eggs are deposited next to the midvein or large lateral veins, and are slightly embedded into the leaf tissue on the abaxial leaf surface. One larva lives in each leaf gall, but two or more galls may develop next to each other. Maximum leaf gall length (∼2.0 mm) occurs by late May. Larvae completely consume the moist nutritive tissue, leaving only a thin gall layer around the final instar. Pupation occurs in May and adults exit in late May or early June.

Plagiotrochus cornigerus O. S. Bisexual form

Ovoid, whitish leaf galls, 1.5 - 2.5 mm long, along midrib or major veins.

Adults in July.

On Q. rubra, Q. palustris, Q. imbricaria, Q. ilicifolia.

Ovoid, whitish galls, along midrib or larger veins, 1/15 to 1/10 inch long, on Spanish oak, pin and scrub oaks, early summer, sexual generation, gall wasp