On leaf, under side, cylindrical with rounded distal end standing
erect from the cup-like base embedded in the leaf blade. 4-6 mm. high,
generally very close to 5 mm. 1 mm. dia. Body of gall, yellow to brown
in color, distal end reddish to brown, at length almost black. Basal
cup, greenish yellow to dark purple. Cylindrical part of gall smooth
as though polished. Gall attached to the cup only at its central basal
part. Before the end of summer the tube-like portion breaks away with
its enclosed larva. On the side of the leaf opposite the gall its
position is indicated merely by a dark discoloration. Very common on
different kinds of hickories.
Osten Sacken, Lowe’s Monogr. Dip N. Am. Pt. 1, p. 192, 1862.
Felt, Rept. Ins. N. Y. 1907. pp. 382, 388, pl. 37, Fig. 5.
Felt, “Caryomyia tubicola” Jour. Econ. Ent. 4:456. 1911.