Nov 16: My driveway, under 2 Quercus alba (White oak), 3 Q. coccinea (scarlet oak), and a Carya alba (mockernut hickory) is littered with scores of 3-4 inch abscised twig ends with one (or occasionally two, opposite) galls like this. The galls are hard and of uniform size and have no holes in them.

Dec 09, 23 days later: I used a kitchen knife to cut open one of the above 13mm galls. It contained a 3.2mm white legless larva in a smooth sphere, a ball of tan granular excrement that held into a ball, and silk.