Callirhytis milleri, new species

Host. — Quercus agrifolia Née, Quercus californica Cooper, Quercus wislizeni A. de Candolle.

Gall. — A compact stony-hard mass containing four to a score or more confluent cells inside of and in Agrifolia and Wislizeni acorns more or less filling the interior of the acorn, which is frequently reduced in size (fig. 2). The woody mass thus occupies the center of the acorn instead of the cotyledons, extends its whole length, and when the acorn is cut open can be lifted out intact. In California the acorns are of normal size and the cotyledons are present but distorted. Occurs in late summer or fall in acorns of current season's crop. See notes on Biorhiza eldoradensis (Beutenmüller), p. 7.

Habitat. — The type locality is Pacific Grove, California, where affected Agrifolia acorns were collected November 15, 1913, by Mr. J. W. Miller, who reared 20 adults March 8-27, 1915, sent in with galls under Hopkins U. S. No. 10867b and for whom the species is named. The writer collected some at Palo Alto, August 10, 1915, and cut out a pupa September 17, 1917, and a living fly December 19, 1917, indicating that transformation takes place the fall before emergence. The writer has also taken the galls at Alpine, Pasadena, Santa Barbara, Paso Robles, Los Gatos, and St. Helena, California. The writer found similar galls in old Wislizeni acorns at Camp Baldy, June 15, 1918, and living adults were cut out December 2, 1919, and an equal number of larvae found indicating that the emergence is distributed over at least two seasons. These flies agree with those from Agrifolia acorns except that they average 2.6 mm instead of 2.8 mm in length. Similar ones were seen in the San Gabriel River canyon in the San Gabriel Mountains and at Bagby in the Sierras. Mr. F. H. Herbert sent in similar galls in acorns in California from Onion Valley, in El Dorado County, under Hopkins U. S. No. 13643c and from Los Gatos under Hopkins U. S. No. 13673e. From the latter, five flies emerged March 31 to April 15. They are similar to the others except in being larger, averaging 3.1 mm, and they are included in the type series.

- LH Weld: (1922) Notes on American Gallflies of the Family Cynipidae Producing Galls on Acorns: With Descriptions of New Species^©

Reference: https://www.biodiversitylibrary.org/page/7305399#page/485/mode/1up