136 Journal New York Entomological Society. [Vol. xxiv, 



long spines on anterior coxje and the labium whitish. Legs greenish testaceous, 

 paler beneath, the tarsi infuscated and the claws black. Abdomen yellowish, 

 copiously but not densely clothed with short, black hairs. Wings clear, the 

 costal veins and bases of the longitudinal veins black, the first longitudinal 

 vein ending in the costa above the second crossvein and considerably before 

 the first crossvein, the costal border of the marginal cell a little less than 

 twice as long as the costal border of the first submarginal cell and the first 

 basal cell as much longer than the second basal cell as the length of the 

 second crossvein. 



Type. — Juan Viiias, Costa Rica, March 15, 1902, on a stimmer 

 tanager (Piraiiga rubra) by L. Bruner. 



This species is apparently closest to O. haiticusis Bigot, with 

 which it agrees in the dark hair on the antennary processes and the 

 first longitudinal vein ending in the costa before the first crossvein, 

 but differs in its smaller size (haitiensis is 7 mm. long), in the form 

 of the clypeus (Jiaitioisis has a small dorsal pit but a large and deep 

 angular anterior pit) and in the coloration (haiticusis has a large, 

 well-defined, cordiform mesonotal area, a black ocellar spot, etc.) 

 It differs at once from 0. erythroccphala Leach and O. hellardiana 

 Rondani in the dark instead of ferruginous hairs on the antennal 

 processes. Its small size separates it at once from the described 

 North American forms except O. but alls (which has a very different 

 coloration), O. auchiucuria (which has the basal cells of subequal 

 length) and O. fuscivcutris (which has the head and mesonotum uni- 

 formly colored). 



The three species of OruitJiomyia above described may be sep- 

 arated as follows: 



Hair on antennary processes ferruginous. 



Head yellowish brown, the- mesonotum fuscous brown buteonis. 



Head bright ferruginous, the mesonotum blackish costaricensis. 



Hair on antennary processes dark pirangae. 



