Acraspis erinacei (Hymenoptera: Cynipidae)
Hedgehog Gall
Cornell Plantations, Ithaca, Tompkins County, New York
July 6, 2007

Identified with the help of Kathy Schick and Cynipid Galls of the Eastern United States by Lewis H. Weld (1959). The gall in this photo is 7mm in diameter; they grow up to 13mm. On Quercus alba (white oak).