386 NORTH AMERICAN DIPTERA 



The Stable Fly {Stonioxys calcitrans) is a biting insect and is 

 sometimes known as the Biting House Fly. It is not a general visitor 

 in houses but may ])e common in yards and on porches near stables, 

 and is most active in the hot sun. It is also a pest on beaches and along 

 streams on bright, sunny days. It breeds in manure and decaying vege- 

 tation so may be controlled by measures taken against the House Fly. 

 Domestic animals suffer greatly from its bites and milk production may 

 be greatly reduced when the fly is abundant. The flies enter the stable 

 on cattle and horses and many of them remain there over night. Use of 

 a fly spray in stables will greatly reduce their numl^ers. The view has 

 been expressed that infantile paralysis is carried by this fly but the ac- 

 cusation has not been proved. However, under certain conditions it 

 may transmit sleeping sickness. 



The Horn Fly {Lyperosia irritans) so named because of its lial)it 

 of feeding about the base of the horns of cattle, is also a biting fly. It 

 rarely attacks man. 



The classification of this family is still in an unstable condition and 

 it is seldom that two authors use tlie same generic limits and very fre- 

 quently different names are used for the same generic concept. Un- 

 fortunately several of the genera are not available for study and I 

 have been forced to include about a score of them from descriptions 

 only, while four of those recorded from North America are excluded. 

 A half dozen genera occurring in South America and not yet recognized 

 from our region are keyed out as it is likely that they occur in the 

 tropics. In one or two cases the characters I have used will change the 

 limits of genera, and I have recognized as genera groups sometimes con- 

 sidered to be no more than subgenera. 



In order to facilitate the use of the Key I have prepared a synoptic 

 key leading to the main subdivisions employed. 



SYNOPTIC TABLE 



A. With at most one sternopleural bristl? 1 



With two or more sternopleurals B 



B. Anal vein extending to the wing-margin 39 



Anal vein not extending to the wing-margin C 



C. Arista plumose, pubescent or bare D 



Arista pectinate, without rays below 144 



D. First vein setulose on most of its length 77 



First vein bare bevond the humeral crossvein E 



