Collected from _H. alba_ and _H. ovata_, July and August. Felt, Jour. Econ. Ent. 4:456. 1911. 21. =Caryomyia holotricha= O. S. On leaf, under side, large tawny, long-haired galls, distributed singly (Fig. 21) or massed (Fig. 21a) on the leaflet. When massed they form a conspicuous brown, hairy structure, suggesting a huge caterpillar. The isolated galls are sub-globular to round-conic with or without a small terminal nipple. 3-5 mm. vertical diameter, 3-5 mm. wide. Interiorly the chamber of the isolated form is depressed, this fact being associated with that of the thick distal wall. Gall chamber surrounded by definite sclerenchyma layer. Cortical tissue firm. Attached by irregular process from leaf extending into base of gall. In the massed forms, the galls are similar in structure, but are variously shaped, due to mutual pressure, (Fig. 21b). Compactly attached to the common central hyperplasia along the vein, which on the upper side of the leaf is a reddish irregular, low elevation. Some of these masses are as long as 5 cm., possessing a thickness of 10-15 mm. Common on various hickories, particularly _H. ovata_. A gall which may eventually prove to be a different species but which here is provisionally classed as a variety of _C. holotricha_, was found in numbers on the leaves of _H. alba_, though it is probably not restricted to this species of hickory. Instead of an apical nipple, it has an apical pit, which is choked with the characteristic brown pubescence of this type of gall. Internally a tuft of coarse brown trichomes extends inwardly from the distal side of the chamber. The chamber occupies the proximal one-half to two-thirds of the gall, the wall over it being uniformly very thick. This type of gall is constant, being collected repeatedly and examined minutely. Based on Felt’s brief description, his _Caryomyia thompsoni_ Felt was taken from this gall or one very similar to it. Closely allied to the above variety is another form, with internal tuft of trichomes, in which the apical nipple is present. The layer of tissue lining the chamber appears very white, due probably to the character of the tissue beneath the superficial nutritive layer. In section the thin white chamber wall is very definitely delimited from the adjoining darker tissues. Many of these conic-sub-spheric galls were 6 mm. in width. Collected on _H. glabra_. Types of this and the above variety are at the Ohio State University. Osten Sacken, Lowe’s Monogr. Dip. N. Am. Pt. I, p. 193. 1862. Felt, “Hormomyia holotricha” 23rd Rept. Ins. N. Y. 1907. pp. 382, 389. Felt, “Caryomyia holotricha” Jour. Econ. Ent. 4:456. 1911. 22. =Cecidomyia= sp. =Cecidium= nov.