Cynips bella, n. sp.

These belong to the class known as oak-apples. They are attached by a minute sessile point to the under side of the leaves of an oak found in Arizona--often near the margin of the leaf, but more commonly on or near the mid-vein. They are perfectly round, and those that have escaped the attack of parasites are quite uniform in size, measuring from 3/4 to 7/8 of an inch in diameter. Those stung by parasites are generally much smaller, and this species is so subject to their attacks that more than three fourths are thus affected. The galls (when dry) are of various shades of brown, mostly smooth but not polished; a few specimens have a decidedly russet color and a rough surface. The shell very thin and brittle. Each gall contains a single larval cell which is kept in a central position by fine, silky, radiating fibers, that reach from it to the outside covering. Besides these fibres, there are others that are attached to the inner surface of the shell, but which are not attached to the larval cell. They are much finer than the others and resemble coarse wool. Except that these galls are smaller, and the internal structure more delicate, and the surface less smooth and polished, they might easily be taken for those found on Quercus rubra--C inanis.

- HF Bassett: (1881) New Cynipidae (1881)^©

Reference: https://www.biodiversitylibrary.org/item/22092#page/103/mode/1up