A small, nearly flat disc at the edge of an unidentified red oak leaf. It resembles the California endemic Acraspis guadaloupensis, and its raised rim forms a tight seam against the leaf, suggesting that like A guadaloupensis it might be detached from the leaf, but is in fact integral, showing the same seams on both sides. The center of the disc bulges out from either side as if vacuum-sealed around its contents (presumbly the larval cell). Every gall of this type observed so far has been found directly abutting the edge of the leaf.

A fresh gall matching this description was seen on Quercus rubra in Michigan in May and June (2). Insects (inducers or parasitoids) had already emerged from galls found in July (2) in Pennsylvania. Emergence holes were seen on the upper or lower side of the leaf. Old galls have also been seen in Pennsylvania in October.