104 NORTH AMERICAN DIPTERA. 



3. Second basal cell as long or but little shorter than the first. 



PHYTOMYZA Fallen. 

 Second basal cell distinctly shorter than the first (Agromyzince). 4 



4. First posterior cell narrowed at the margin. . LEIOMYZA Meigcn. 

 First posterior cell not narrowed at the margin, the third and fourth 



longitudinal veins nearly parallel 5 



5. Third antennal joint terminating in a spiny point. 



CERATOMYZA Schiner. 

 Third antennal joint does not terminate in a spiny point. . . 6 



6. Third antennal joint rounded, of moderate size.* AGROMYZA Fallen. 

 Third antennal joint very large, subquadrate in shape. 



PHYLLOMYZA Fallen. 



7. Second basal cell united with the discal cell 8 



Second basal cell separated from the discal cell by a small cross-vein. 9 



8. Arista wholly wanting CRYPTOCH;ETUM Rondani. 



Arista present, bare; cross-veins remote, the anterior one situated near 



the base of the wing. . . . AULACIGASTEU Macquart. 



9. Oral vibrissae present; abdomen short and broad (Milichinet). 10 

 Oral vibpissae wanting; the abdomen elongate oval (Ochtliiphilimr). 12 



10. Costa with a deep incision before the tip of the first vein. 



LOBIOPTERA Wahlberg. 

 Costa not with sucb an incision 11 



11. Eyes round; mesonotum with bristles in the middle. MILICHIA Meigen. 

 Eyes oval; mesonotum with bristles on the sides only. 



CACOXENUS Loew. 



12. Front with long bristles on the sides. . . OCHTHIPHILA Meigen. 

 Front without bristles on the sides. . . . LEUCOPIS Meigen. 



35. GEOMYZID.E. 



Head rounded; face usually with vibrissae; front broad, 

 bristly below the vertex. Antennae short, the third joint 

 round or a little elongated, with a bare, pubescent or plumose 

 arista. Wings comparatively long ; auxiliary vein rudimen- 

 tary ; posterior basal cell and the anal cell present. 



* The genus Desmometopa Loew has never been described, but will be 

 included in Agromyza ; I do not know it. 



