NORTH AMERICAN DIPTERA. 



3. Costal vein and front destitute of strong setae. Gymnophora. 

 Costal vein and front provided with strong setae. ... 4 



4. Anterior frontal setae reclinate, middle tibiae with one or more 



setae on the outer side near the base.j . . . Phora. 

 Anterior frontal setae reclinate, middle tibiae destitute of such 



setae, ovipositor hard and polished. . . Apocephalus. 

 Anterior!" frontal setae proclinate, middle tibiae destitute of such 



setae Aphiochseta. 



5. First longitudinal vein wanting. . . . Ecitomyia, male. 

 First longitudinal vein present as usual. .... 6 



6. Anterior frontal setae reclinate, middle tibiae with one or more 



setae on the outer side near the base. .... 7 



Anterior frontal setae proclinate, middle tibiae without such setae. 9 



7. Velvet black, middle tibiae of the male with a row of long set?e on 



the upper side Trineura. 



Not velvet black, middle tibiae with only two or three setae besides 

 those at apex. ......... 



8. Male antennae prolonged into a slender point with apical arista. 



Female antennae with a slight point where the arista is inserted 

 at the upper corner, seventh vein obsolete. . Conicera. 

 Third joint usually rounded in both sexes, seventh vein distinct. 



Hypocera. 



9. Spurs of four posterior tibiae wall developed. . 10 



Spurs of middle tibiae wanting, those of posterior pair minute, n 



10. Ovipositor of female prolonged, stout and thickly chitinized, ven- 



ation of wing normal. .... Plastophora. 



Ovipositor fleshy and retracted as usual, first and third veins 



strongly approximated, legs stout. . . . Syneura. 



11. Fourth, fifth and sixth veins light, seventh wanting; four trans- 



verse rows of frontal setae Metopina. 



Fourth, fifth, sixth and seventh veins strong; three transverse 

 rows of frontal setae Puliciphora. 



12. Wings present, although of very small size. . . 13 

 Wings completely absent. ..... 16 



13. Wings small, strap-shaped, often bearing long bristles. 14 

 Wings larger, indistinctly veined, more or less triangular in shape. 



Commoptera, female; 



