56 



DIPTERA OF NORTH AMERICA. 



[PART III. 



it, is exactly the same as that of Systata to Ortalis. The color- 

 ing and the picture of the wings resemble those of the first section 

 of Pteropsectria, only the obscure borders of the crossveins coalesce 

 more or less, on account of their proximity, into a single cross- 

 band. 



Typical species: lacustris Meig. 



9. Pteropsectria Lw. 



Charact. — Eyes large, elongate ; front but very little projecting, face rather 

 strongly carinate ; cheeks narrower than in most other genera. 



Hairs on the body of the usual length ; the middle of the thoracic 

 dorsum bristly on its posterior portion only. 



Third antennal joint more or less elongate, rounded at the end; 

 the second very much shorter. j 



The crossveins are at the usual distance from each other; the 

 first longitudinal vein has bristles upon its end only. 



This genus contains small, shining black species, the thorax of 

 which shows only a faint trace of pollen. The picture of the 

 wings generally consists in the dark color of the costal and sub- 

 costal cells, a more or less distinct black border of the crossveins 

 and a black spot on the costa, lying a little before the apex, or 

 upon it ; in some species, however, this picture expands into four 

 crossbands which are connected, two and two, near the costa. 



The genus is divided into two sections, which may even be 

 considered as separate genera. They are easily distinguished by 

 the picture of the wings, which is in keeping with a corres- 

 ponding difference in the rest of the organization. 



Sect. 1. {Pteropsectria, sensu strict.) with spotted, or incom- 

 pletely banded, wings. 



Typical species : palustris Meig. 



Sect. 2. (Tliryophila Lw.) ; bands on the wings complete. 



Typical species: frondescentise Lin. 



10. Tephronota Lw. 



Charact. — Third antennal joint, although not excised on the upper side, 

 still with a sharp anterior corner. 



Thoracic dorsum, upon its middle, not bristly in front of the 

 region of the suture. 



First longitudinal vein bristly upon its end only; the fourth not 

 bent forward ; the posterior angle of the anal cell not prolonged in 

 a lobe. 



