182 NORTH AMERICAN DIPTERA. 



2. One sternopleural bristle ; wings without spots. ....■] 

 No sternopleural bristle; wings with round, brown spots. 



Ernoneura Becker. 



3. Front tibije with a terminal, short rectangularly spine (in addition to 



the ordinary bristles). .... Acanth^'X^nema Becker. 

 Front tibiae without such spine .^ Y^ . 4 



4. Hypopygiuni with long tufts of hairs. ...... 5 



Hypopygiuni without long tufts of hairs. ..... 8 



5. Third antennal joint somewhat elongate, angulated at the tip ; oral 



border with numerous, closely placed bristles. ... (3 



Third antennal joint short, rounded at tip; oral border with two remote 



bristles. Bostrichopvga Becker. 



G. Wings with two supernumerary cross-veins. Pogonota Zettcrstedt. 

 Wings not with supernumerary cross-veins. . Okenia Zetterstedt. 



7. First posterior cell closed Lasiescelus Becker. 



First posterior cell open or but little narrowed. .... 8 



8. Much elongated species. ........ 



Short or but little elongated species. ...... 10 



9. Middle and hind femora of the male strongly thickened. 



St.egeria Rondani. 

 All the femora slender Cosmetopus Becker. 



10. Third antennal joint rounded distally. . Micropresepa Becker. 

 Third antennal joint angulated distally. . . . . .11 



11. Mesonotum and legs thickly hairy. . . Spathiophoka Rondani. 

 Mesonotum and legs thinly and not long hairy. . . . . l:i 



12. Antennae small, abgulated at tip; arista thickened at base ; small, sliort, 



gray species. ...... Tricopalpus Rondani. 



Antenna} large, broad, rounded at tip ; arista thickened to near the tip. 



Acekocxema Becker. 

 cleioastrin^t;. 

 1. Five dorsocentral, two scutellar, one posthumeral bristles; black 



species Cleigastra Macquart. 



Two or three dorsocentral, front scutellar and two post-humeral bris- 

 tles; honey-yellow species. . . Gimvo.mera Rondani. 



NORKhlA'SM. 

 1. Front femora with two rows of strong bristles, the outer ones long and 

 strong, the inner ones short. . . . Norei-lia R. Desvoidy. 

 Front femora with four spines, bristles on the outer side only. 



Ac/:ANTnoLEXA Rondani. 



