244 NORTH AMERICAN DIPTERA 



KEY TO GENERA 



1. Fourth vein furcate "* 



Fourth vein not furcate 2 



2. Discal cell closed apically 3 



Discal cell open 5 



3. First vein bare; third antennal segment elongate conical (8, 11, 12). 



*Agathomyia Verrall 

 First vein setulose above; third antennal segment rather short (2, 

 3, 13 ) tCallimyia Meigen 



4. The fourth vein branches close to the posterior crossvein, the posterior 



branch reaching the wing margin (10) Platypezoides Johnson 



The fourth vein branches nearer to the wing margin than to the pos- 

 terior crossvein, the posterior branch not reaching the wing margin 

 (4, 5, 6, 7) 'Tlatypeza Meigen 



5. Third vein obsolete except apically (9) Microsania Zetterstedt 



Third vein complete; three closed cells (1) Platycnema Zetterstedt 



* Johnson, 1923, Occ. Pap. Best. Soc. Nat. Hist., v, pp. 51-58. 

 t Johnson, 1916, Psyche, xxiii, pp. 27-33. 



