236 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 59. 



little longer than broad, distal two-thirds stout. Pronotum coria- 

 ceous on sides. Mesoscutum slightly longer than broad, coriaceous 

 with distinct smooth parallel and lateral lines and well-separated 

 parapsides obsolete anteriorly and in which are a few scattered punc- 

 tures visible in balsam, separated from scutellum by a distinct suture. 

 Scutellum rugose, with arcuate reticulate furrow at base. Propo- 

 deum with two parallel carinae inclosing a smoothish area in which 

 is a faint median ridge, spiracular areas reticulate. Legs with hind 

 tarsus shorter than tibia, claws simple. Wings with distinct brown 

 veins, first abscissa of radius arcuate, areolet indistinct, surface pu- 

 bescent, margin ciliate, a transverse clouded area extends from 

 origin of radius nearly across wing, first cross-vein also slightly 

 clouded. Abdomen strongly compressed, as deep or deeper than 

 long, smooth and shining, hypopygium prominent with ventral spine 

 about as long as broad, ventral valves protruding obliquely, ovipos- 

 itor when dissected out longer than antenna, ovarian eggs well 

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

 ratio is 1.25; antenna, 2.28; ovipositor, 3.1; wing, 3.4. 



Length of 8 pinned specimens 1.7-2.1 mm. Average, 1.9 mm. 



Type.— Cat. No. 22579, U. S. N. M. Four cotypes. 



Host. — Quercus fondleri Liebmann. 



Gall. — A slight gradual enlargement at crown of small saplings 

 which are 3-15 mm. in diameter. The larval cells are not scattered 

 uniformly but occur in nests of three or four to a dozen cells under 

 the bark in a sort of depression or pocket in the wood. 

 The cells are white, brittle, thin-walled, about 2-3 mm. in diameter. 



Type locality. — Trinidad, Colorado. The type galls were collected 

 July 10, 1916. They then contained pupae, and when cut open 

 September 16 living flies were obtained. Natural emergence date un- 

 known. Similar but larger old galls were collected at Las Vegas, 

 New Mexico. 



34. COMPSODRYOXENUS HUMILIS, new species. 



Female. — Nearly black; head, thorax, base of abdomen more or 

 less brownish. Head broader than thorax, interocular area 1.1 times 

 as broad as high, malar space nearly 0.4 eye and with parallel striae, 

 palpi 5- and 3-segmented, antennae 13-segmented, first, fourth and 

 fifth subequal, third slightly longer than first, last twice as long as 

 preceding, flagellum darker distally. Pronotum coriaceous. Meso- 

 scutum broader than long, coriaceous, parapsides faint, broadly 

 separated behind. Scutellum rugose, with arcuate furrow at base 

 without septum and not limited laterally, slightly margined behind. 

 Propodeum with usual parallel ridges and a distinct median. All 

 last tarsal segments infuscated, claws weak, simple, divergent. 

 Wing with distinct dark veins, first abscissa of radius arcuate and 

 about half length of second, areolet present, first cross-vein heavily 

 clouded, large transverse cloud in radial area, surface pubescent, mar- 



