Callirhytis middletoni, new species

Host. — Quercus phellos Linnaeus.

Gall. — Green, 6 by 7 mm. and 5 mm. thick, surface rough with blunt warty elevations, apex slightly prolonged, monothalamous, wall 1 mm. thick. They drop from the twigs in early May. No investigation was possible and it is not known whether this is a bud or acorn gall. The fly is so closely related to species from pip galls on young acorns that it seems probable that this is an acorn gall. After the galls drop an outer fleshy layer decays away, leaving a stony shell with sharp longitudinal ridges.

Habitat. — The type locality is Washington, District of Columbia. This gall was first called to the author's attention by Mr. J, C. Crawford May C, 1914, when a large number of galls were collected on the ground under a large tree on the Mall between the Natural History Building of the United States National Museum and the Smithsonian Building. The author, however, failed to rear it. On the same date Mr. William Middleton collected galls from same tree. Adults emerged April 9 and April 16, 1915, and one April 17, 1916. These are recorded under Hopkins U. S. No. 12036. Mr. Middleton had also collected galls under the same tree May 2 and May 10, 1912, and pupae were found in the galls in September, 1913, and adults in November, 1913. The flies emerged March 31, 1914. The species evidently transforms in the galls that fall and adults emerge the next spring, the emergence being distributed over two seasons. Galls collected under same tree April 29, 1920, gave adults in the latter half of March, 1921. The new galls on this tree began to drop by April 15, 1921.

Callirhytis middletoni

Quercus laurifolia, phellos
Acorn galls
A pip gall dropping in early May after which an outer fleshy later decays leaving a hard shell with a rough surface as in photo.

[Photo caption]
On Q phellos. Galls drop in early May (DC) and an outer layer decays leaving a hard shell as in photo. Adults emerged the next spring Apr 9-16 and the second spring Apr 17.