Cecidomyia niveipila n. sp.

Deformation of oak leaves, consisting of a large fold with a white pubescence on the inside. It begins very early in the spring on the young leaves of the white oak and other kinds of oak. The egg is probably deposited on the upper surface of the leaf, on one of the ribs. The irritation caused by the larva produces a fold or cavity in the leaf, lined inside with a white pubescence. The under side of the leaf shows on the corresponding spot the swollen rib, which is pale green, bordered on both sides by the same white pubescence. The galls, according to their size, contain more or less larvae, sometimes ten or more. When this deformation is very large, it involves the whole leaf, which is folded in two along the midrib, the under side forming the outside of the fold, and showing the swollen ribs with the white pubescence in their intervals. On the 25th of May I found some of the galls considerably grown, thick, and swollen; their pubescence was of the brightest white; the larvae they contained were also grown, plump, white. Other galls, on the contrary, had grown but little, and appeared sickly or withered. They contained no larvae at all, or their inmates appeared yellowish and sickly.

- Baron Osten Sacken: (1862) On the North American Cecidomyiidae^©

Reference: https://www.biodiversitylibrary.org/page/28363390#page/232/mode/1up