MUSCIDiE. 343 



12. Posterior dorsocentral and acrostical bristles well-developed and 



constant; cheeks hairy; third longitudinal vein spinulose at base 



only. Oalliphora. 



Posterior dorsocentral and acrostical bristles constant and well- 

 developed; cheeks bare; first section of the third vein lor a part 

 or all its length spinnlose. ..... Lucilia. 



13. Posterior dorsocentral and acrostical bristles inconstant and une- 



qually developed; cheeks hairy; first section of third vein in 

 large part spinulose. ...... Phormia. 



Posterior dorsocentral well, the acrostical bristles unequally de- 

 veloped, cheeks hairy; first section of third vein in large part 

 spinulose. ...... Protocalliphora. 



14. Middle tibiae with a prominent bristle on its inner, flexor surface 



beyond the middle. . . . . . . . . 15 



Middle tibiae without such bristle. . . . . . 17 



15. Termination of first longitudinal vein nearly opposite the middle 



of the penultimate section of the fourth vein; distal section of 



the latter forming a broad curve. . . Mesembrina. 



Termination of first vein nearly opposite the anterior cross-vein. 16 



16. Sternopleurae with one bristle in front and two behind; angle of 



fourth vein rounded. .... Pseudopyrellia. 



Sternopleuraae with one bristle in front and three behind; last sec- 

 tion of fourth vein forming a broad, gentle curve. Pyrellia. 



17. The last section of the fourth vein has a rounded angle; sterno- 



pleurae with one bristle in front and two behind; never metallic 



species Musca. 



Last section of fourth vein broadly curved near its middle, or with 

 an anterior flection at its tip. ...... 18 



18. Eyes pubescent. ......... 19 



Eyes bare. .......... 20 



19. Antennae separated at their base by a distinct carina; sternopleu- 



rae with two bristles behind, none in front; body gray or partly 

 rufous with a well-defined black pattern (5). Graphomyia. 

 Antennae not separated at base by carina; sternopleurae with two 

 bristles in front and two behind; body not metallic colored. 



Myiospila. 



20. Last section of fourth vein with a broad curvature near its middle. 



the cell opening rather narrowly; grayish or metallic spotted 



species (7,8) Morellia. 



Last section of fourth' vein curved forward, often slightly, beyond 

 its middle or at the tip, the cell broadly open. . . 21 



21. First longitudinal vein ends beyond the middle of the wing; one 



or more well-developed pairs of anterior acrostical bristles (9). 



Muscina. 



The first vein ends before the middle of the wing; no anterior 



acrostical bristles (10). . Clinopera. 



Somomyia, Cyrtoneurina and Hyadesimyia are not included in the 

 table, because of insufficient data. 



