2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 69 



The genus forms a typical case of Brauer's character of the vibris- 

 sa! angles narrowing the clypeus, as the vibrissae are close together 

 and high up, only a little below the middle of the head in profile, 

 while the median space below them is greatly narrowed for a con- 

 siderable distance. Antennae rather short and resting in a depres- 

 sion; arista bare or slightly pubescent. The parafacials have scat- 

 tered distinct short hairs. Eye very small, so that there is an enor- 

 mous area below it, bare and usually concave, the cheek or bucca at 

 least equal to the eye in height. Head moderately long above but 

 short at the oral cavity, the profile receding, especially below the 

 vibrissae. Proboscis small, palpi rather small. The wing has a 

 strikingly long stump at the bend of the fourth vein, and the first 

 posterior cell is open, ending before the tip of the wing. Veins bare 

 except for a few hairs at base of the third vein. 



Related American genera, as far as represented in the National 

 Museum, may be tabulated as follows : 



KEY TO AMERICAN GENERA BELATED TO MICROPHTHALMA 



1. Fourth vein straight beyond the hind cross vein, with distinct stump or 



branch at the bend ; discal bristles absent 2 



Fourth vein curved backward beyond the hind cross vein, with rounded 

 V-shaped bend and no branch 4 



2. Arista plumose (type caninum Fabricius) Dexiosoma Rondani. 



Arista bare or pubescent 3 



3. Abdominal sternites bearing clusters of spiny bristles (type rufiventris 



Macquart) Megaprosopus Macquart. 



Abdominal sternites without spiny bristles (type uigra Macquart), 



Microphthalma Macquart. 



4. Front not prominent, head lenticular in shape (type opaca Townsend), 



Megapariopsis Townsend. 



Front prominent, nearly horizontal (type mexicana Brauer and Bergenstamm, 



synonym of calogaster Bigot) Macrometopa Macquart. 



I have redescribed the genotypes of Megaprosopus and Macrome- 

 topa in Annals of the Entomological Society of America (vol. 17, 

 1924, p. 211). 



KEY TO SPECIES OF MICROPHTHALMA 



1. Third antennal joint black, usually reddish at base about to the arista— 2 

 Third antennal joint red, sometimes slightly infuscated at tip 4 



2. Small cross vein not infuscated, wings hyaline (Peru)___ cuzcana Townsend. 

 Small cross vein infuscated, wings decidedly clouded basally 3 



3. Tip of first antennal joint produced above into a scale projecting over and 



beyond the base of the second joint (Guatemala to New Mexico) 



nigra Macquart. 



Tip of first antennal joint not produced (Peru) virens, new species. 



4. With only two sternopleurals ; smallish, rather slender species, front of head 



wholly red ruficeps, new species. 



With three sternopleurals 5 



5. Abdomen with silvery or white crossbands on basal third or half of segments 



2, 3, and 4, the remainder of the segment more polished black, contrasting 



(U. S., widespread) disjuncta Wiedemann. 



Abdomen entirely pollinose, not with contrasting crossbaud 6 



