Cynipidae [tentatively taken to be A cookii]

Quercus rubra, coccinea. MA. Sept-Oct. Soft, inanis center; purple-brown. Some are keeled on twigs

Amphibolips cookii

Quercus rubra
Bud galls
Spherical, 11-25 mm in dia, spotted, dropping when full-grown in early Sept. and becoming wrinkled.

[Photo caption]
An immature gall on Q rubra. They are spotted when full-grown, 11-23 mm in dia, wrinkled after dropping. Brodie put 187 galls on ground over winter and fifty adults emerged the next Oct 25 and oviposited in buds on Dec 1 (Toronto). Miss Knox at Cornell reared the maker Oct 29-Nov 4. 54% of the galls were parasitized. The acorn moth, Valentinia glandulella was in 23% of the galls, the maker in 14.5%. Eight species of chalcids were reared and a guest cynipid, Synergus sp. emerged May 22 after a pupal period of 10 days from chambers formed in the central cell. Occurs on velutina too.

Amphibolips cookii

Globose, slightly nippled, green, spotted with red, becoming brown, moderately thick-shelled twig or bud gall, with a fiber-supported, central cell, diameter 16 to 18 mm, on Q rubra in September and October.

Amphibolips cooki

Amphibolips cookii

Gall. Issuing from a bud on the terminal twigs of red oak (Quercus rubra) in September and October. Almost globular and usually with a small nipple at the apex. Green and succulent and spotted with red when fresh, and with the outer shell moderately thick. Internally with a central larval cell held in position by radiating fibers. When old the gall becomes brown and shriveled in appearance. Diameter about 16 to 18 mm.

The gall somewhat resembles that of A inanis, but differs by being smaller, a thicker outer shell and much stouter radiating fibers. It is an autumnal species and the galls readily break off when touched, or it falls with the leaves or before them. It is a bud gall, while that of A inanis occurs on the leaves in spring. The adult emerges late in August and early in September.

Habitat: CT, NJ, NY, NC, PA, MI, IO