Dryocosmus deciduus

Quercus coccinea, falcata, ilicifolia, imbricaria, marilandica, rubra, velutina
Leaf galls, detachable
Black Oak Wheat. Cluster of up to 40 bursting out of midrib in early Oct, dropping when mature.

[Photo caption]
On Q velutina. Also on Q coccinea, ilicifolia, imbricaria, rubra, falcata, marilandica. Adults emerged Mar 13- Apr 22 the second spring (IL). Galls burst out of a crack in the midrib in a group and drop early in Oct. Dr Hopkins referred to them as "black oak wheat" as poultry were feeding on them. They are said to contain 63.9% carbohydrates and 9.34% protein. The photo is of isolated galls after a winter outside in breeding cage.

Dryocosmus deciduus

Black oak wheat. Individual galls about size and shape of a kernel of wheat with a fleshy knob at upper end, greenish, smooth, bare. When young concealed in the swelling midrib but later bursting out of a crack in a compact cluster of from a few to 40 galls often rupturing the leaf blade so as to be visible from above, dropping in Oct. On Q. rubra and velutina. Galls collected in Oct. 1916 gave adults Mar. 23-Apr. 22, 1918.

Andricus decidua, new species

Cynips quercus decidua
Cynips decidua

Gall : On the midribs of the leaves of red oak (Quercus rubra) and black oak (Q. velutina). Rounded or elongated swellings filled with oblong kernels from a few to about 40, all depending upon the size of the gall. When young these bodies are concealed in the hard, fleshy part of the gall and as the swelling grows older the seed-like kernels gradually protrude therefrom and when fully grown late in September and early in October the swelling bursts open completely and the kernels fall to the ground. The gall is green when fresh and the kernels are whitish, yellowish, sometimes tinged after they become exposed.

Habitat: New England States, Middle States, and southward to at least North Carolina and westward.

This singular species was hitherto known by the gall only. Described from a single female from the Black Mountains, North Carolina, altitude 3,500 feet. The gall is quite common, but the imago is difficult to raise.

Cynips quercus decidua, n. sp. [described from gall only without insect]

Quercus rubra.

Clusters of seed-like bodies, often thirty or forty together rowing on the midvein on the under side of the leaves of Q. rubra. The larger cells are about the size of a grain of wheat. They are smooth, greenish-white, the apex enlarged, and would remind a botanist of the sessile stigma of some flowers. Gall fly unknown.

My specimens were collected about the first of October, and were then fully grown. Some had fallen to the ground, but on cutting open a large number I could not detect any larvae. The leaf stems and twigs were placed in water to keep them green, but the galls soon dried and many fell off. A few fell into the water, and these not only kept green, but on opening them a few days since, half-grown larvae were found. From this I infer that the growth of this species is dependent upon the galls being covered in the earth.

Dryocosmus deciduus

Andricus decidua

These galls long known in literature under the name decidua before the adult was reared are the ones to which Dr A D Hopkins referred under the name of "black oak wheat" in a note. These specimens were from Wescott, Mo., and Texarkana, Ark. Doctor Hopkins collected galls at Kanawha Station, W. Va., September 25, 1923. The writer collected galls at Evanston and High- land Park, IL.; Ironton and Poplar Bluff, Mo., and at Bluemont, Va. Galls collected at Evanston on October 8, 1916 contained pupae on September 22, 1917 and adults on November 16 which emerged March 23-April 22, 1918. After the galls drop they change shape somewhat as the thick nutritive layer is used up, becoming distinctly spindle-shaped and only a thin brittle shell is left in the swollen central region. The species is here transferred to Dryocosmus.

Andricus decidua

Rounded or elongate midrib swellings filled with oblong or elongate kernels, a few to 40; when young concealed in the tissues and bursting open in October, on Q rubra, Q velutina.

Kokkocynips decidua (Beutenmueller, 1913) n. comb.

Andricus decidua Beutenmueller, 1913. Insecut. Inscit. Menst., 1: 131-132.
Dryocosmus deciduus (Beutenmueller):Weld, 1926b. Proc. U.S. Nat. Mus., 68: 41.

Gall: galls are multilocular clusters of rounded or elongated swellings on the midribs of the leaves that contain from a few to about 40 oblong larval chambers, depending upon the size of the gall (Beutenmueller, 1913).

Host plant: initially described from red oak (Quercus rubra) and black oak (Q. velutina), but Weld (1959) lists this species from most section Lobatae oaks in eastern North America.

Biology: only known from an asexual generation. The gall is fully-grown by September or October, when it falls to the ground.

Distribution: USA, from New England states southwards at least as far as North Carolina and westwards to the eastern Midwest.