NORTH AMERICAN DIPTKRA. 



The larvae of Muscina have been found in decaying 

 vegetables, dung, fungi and the larvae of various lepi- 

 doptera, a remarkable diversity of habits. The larvae of 

 Graphomyia and Mesembrina have been found in horse 

 and cow dung. 



TABLE OF GENERA. 



1. Proboscis long, slender, directed forward; arista pectinate, or 



sometimes with a few hairs below also. .... 2 



Proboscis not elongate, the labella fleshy and not adapted for 



piercing. . .... 3 



2. Palpi nearly as long as the proboscis (Lyperosia; fig. 146). 



Hsematobia. 

 Palpi much shorter than the proboscis. . . . Stomoxys. 



3. Arista bare; distal section of the fourth vein broadly curved at its 



end Synthesiomyia. 



Arista pectinate. ...... Hemichlora. 



Arista plumose. ......... 4 



4. Hypopleurse with a vertical row of bristles. .... 5 

 Hypopleurse not with a row or tuft of bristles. ... 14 



5. Eyes pubescent Tyreomma. 



Eyes bare. .......... 6 



6. Vibrissal angle at a considerable distance above the oral margin; 



angle of fourth vein rounded or rectangular. ... 7 

 Vibrissal angle near oral margin. ...... 8 



7. Thorax and abdomen with depressed hairs or tomentum among 



the bristles, especially noticeable in the intraalar region; dark- 

 colored, slow moving 'cluster flies' (2, 3) . Pollenia. 

 Thorax and abdomen not with such hairs; mesonotum distinctly 

 striped; bright metallic flies (1). . . Chrysomyia. 



8. Bend of fourth vein angular, or with the angle slightly rounded. 9 

 Distal section of fourth vein with a broad curve ; cheeks bare ; 



rather large flies, reddish or yellowish, with the distal portion 

 of the abdomen metallic (4). . . . Mesembrinella. 



6. Dorsocentral bristles present. ...... 10 



Dorsocentral bristles absent. . . . Chloroprocta. 



10. Arista .usually plumose for not more than two-thirds its length; 



hypopygium prominent. ..... Cynomyia. 



Arista plumose to tip; hypopygium not prominent. . . u 



11. Mesonotum not flattened behind the transverse suture. . 12 

 Mesonotum flattened behind the transverse suture. . . 13 



