16 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.68 



to basal, cubitus reaching basal below middle, its basal half heavier. 

 Radius very heavy, first abscissa angled, second strongly curved 

 toward wnng margin in distal half, radial cell twice as long as broad, 

 partially open at base and apex as well as on margin. Hind tarsus 

 two-thirds as long as tibia, its segments as 47:20:12:7:20 (with 

 claws), claw with a weak tooth at base. Abdomen longer than head 

 and thorax, length to height to width as 58 : 33 : 22, obliquely placed, 

 knife-like on ventral margin, the ventral spine unusually long and 

 tapering, pubescent, as long as hind tarsal segments 1-4. Second 

 tergite occupying nearly or quite all of dorsal margin, its ventral 

 edge forming an angle of 45°, with pubescent area on each side at 

 base. Using width of head as a base the length of mesonotum ratio 

 is 1.6, antenna 3.2, wing 4.5, ovipositor 3.4. 



Range in length, 4.0-5.5 mm. Average of 7 pinned specimens, 

 4.87 mm. 



Separated from other spotted winged species in the genus by the 

 long ventral spine. 



Type.— Cat. No. 27185, U.S.N.M. Type and 2 paratypes. Para- 

 types at Field Museum and Stanford. 



Host. — Quercus arizonica. 



Gall (fiig. 3). — Globular oak apples, up to 35 mm. in diameter, 

 occurring in summer in clusters of sometimes as many as 12 on a 

 twig at apex of previous season's growth. Each has an abrupt slen- 

 der pedicel and usually only 2-4 galls in the cluster become well de- 

 veloped. The fresh galls are creamy white with a reddish blush on 

 one side and spotted with numerous small red spots. Later they 

 become yellowish and are often covered with a bluish bloom. The 

 central cell is supported by a dense mass of fine silky radiating fibers 

 and the wall is thick (0.7 mm.), seven times as thick as that of the 

 smaller unspotted leaf -gall apple of the same region, D. hella. 



Hahitat. — The type fly is one of four bred from galls collected in 

 the Santa Catalina Mountains, Ariz., on " white oak " {Q. arizonica) 

 by M. Chrisman and sent in under Hopkins IT. S. No. 13643w2. The 

 flies were reared November 22 and 27, 1918. Two paratypes from 

 the Huachuca jNIountains are from galls collected in Bear Canyon 

 on Q. arizonica by Ed Jacot, September 28, 1919, and the flies issued 

 before December 3. One paratype is from a gall collected on the 

 same oak by the writer in the Chiricahua Mountains, November 26, 

 1922. The fly had already chewed its way out of the inner cell and 

 was crawling about among the radiating fibers. It remained alive 

 in a pill box without attention until some time after December 31. 

 The writer has collected galls in Arizona at Oracle and in the Sabino 

 Basin in the Santa C.atalinas, and in the Mule, Huachuca, Tnmaca- 

 cori, and Santa Rita Mountains. The galls are even more common 

 on Q. ohlongifolia and at Patagonia were seen on Q. toumeyi but no 



