No. 2368. AMERICAN SUBTERRANEAN GALLS ON OAK— WELD. 215 



margin, anterior and lateral lines enclosed in dark field, median 

 groove a mere notch on hind margin. Scutellum broader than long, 

 truncate and becoming rugose behind, slightly margined on sides, 

 the two smooth quadrate, shallow foveac at base obscured by pubes- 

 cence. Propodeum with two stout parallel carinae inclosing a 

 smooth and nearly square area. Legs with hind tarsus shorter than 

 tibia, second and fifth subequal, tarsal claws simple. Wings with 

 distinct brown veins, third abscissa of subcosta straight not reaching 

 margin, first abscissa of radius angled and with spur, areolet com- 

 plete but small reaching only one-tenth way to basal, cubitus almost 

 reaching basal, surface short brown pubescent, ciliate only on hind 

 margin of hind wing. Abdomen smooth and shining, not com- 

 pressed, second segment occupying over seven-tenths with two tri- 

 angular densely pubescent patches on sides at base and basal two- 

 thirds black. Ventral spine tapering, in balsam twice as long as 

 broad. Ovipositor when dissected out shorter than antenna, ovarian 

 eggs well developed. Using width of head as a base, the length of 

 mesonotum ratio is 1.4; antenna, 1.75; ovipositor, 1.67; wing, 4.0. 



Range in length of 36 pinned specimens, 4.4-5.5 mm. Average, 

 4.8 mm. 



Only female gall-making Cynipid known with 17-segmented 

 antennae. 



Type.— Cat. No. 22566, U.S.N.M. 30 cotypes. 



Host. — Quercus chrysolepis Liebmann. 



Gall. — Large area of greatly thickened bark causing a large swelling 

 at the base of saplings or rough swollen areas at the crown of large 

 trees, especially on callus tissue. This thickened bark contains 

 hundreds of larval cells about 6 mm. long. Such areas also occur 

 where a limb bends over and the elbow touches the ground. The 

 bark becomes over an inch thick and the wood underneath very 

 rough and knotty. On trees in moist gulches. 



Type locality. — Los Gatos, California. The type galls containing 

 living adults were collected November 2, 1918, by Mr. R. D. Hartman 

 and sent in under Hopkins No. 15922 a and placed in rearing at the 

 Eastern Station, East Falls Church, Virginia. The flies emerged 

 April 9, 16, 26, 1919. 



The writer saw old galls in the San Gabriel Mountains on August 

 8, 1916, near Coldbrook camp, and at Camp Baldy on June 17, 1918. 

 Empty galls were also seen at St. Helena, California, on May 28, 1918. 

 On May 13, 1918, while collecting with Mr. Hartman at Los Gatos, 

 galls were found in which there was a thick layer of translucent nutri- 

 tive tissue with no larval cell visible. These were perhaps formed by 

 the flies that had emerged earlier in spring. 



