Gall maker: Cecidomyia poculum O.S; a gall midge (Order Diptera, Family Cecidomyiidae).

Shape and Size: galls are saucer-shaped, and roughly a quarter of a centimeter in diameter.

Location: Usually occur in numbers on the underside of white oak (Quercus alba) leaves.

Color: Covered in white "bloom," hints of brown.

The small, dark indentations in on the pictured leaf indicate where an "oak spangle" has fallen off.