NORTH AMERICAN DIPTKRA. 



6. Third longitudinal vein not furcate. . . . Diadocidia. 

 Third longitudinal vein furcate. ...... 7 



7. Anterior branch of third vein long, terminating in the costa. 



Mycetobiinse. 



Anterior branch of the third vein short, more transverse, usually 

 ending in the first vein. ....... 8 



8. The praefurca of the fourth vein arises from the third vein beyond 



the anterior cross-vein, i. e. the cross-vein is really wanting and 



the third and fourth veins are coalescent for a short distance. 9 



The fourth vein continuous in nearly the same line from the fork 



to its origin from the fifth; cross-vein distinct. Bolitophila. 



9. Antennae short and thick-set, often flattened. . Ceroplatinse. 

 Antennas exceedingly long and slender, longer than the body (4). 



Macrocera. 



SCIOPHILIN^B. 



1. Anterior cross-vein more than twice the length of the basal section 



of the third vein, forming apparently the beginning of the 



third vein (16) Tetragoneura. 



Anterior cross-vein shorter or but little longer than the first sec- 

 tion of the third vein, and forming a distinct angle with the 

 second section. ......... 2 



2. The costal vein terminates at the tip of the third vein (1O). 



Sciophila. 



The costal vein continues a short distance beyond the tip of the 

 third vein. .......... 3 







3. Fork of the fourth vein short petiolate, the prefurca shcrter than 



the anterior cross-vein. . . . Lasiosoma. 



Prefurca of fourth vein much longer than the anterior cross-vein. 4 



4. Proximal end of the posterior furcation (fifth vein) before or op- 



posite the anterior cross-vein (11). . . Neoempheria. 

 Proximal end of the posterior furcation beyond the anterior cross- 

 vein Polylepta. 



MYCETOBIIN^. 



i. Auxiliary vein complete; the anterior branch of the third vein arises 

 at a point where the third vein and the anterior cross-vein unite. 



Mycetobia. 



Auxiliary vein rudimentary, not terminating in the costa; furca- 

 tion of third vein petiolate. ...... 2 



