STABLE-FLIES AND DISEASE 507 



Stonioxys and Disease. — Like the tabanids, the stable-flies 

 are intermittent feeders, i.e., they frequently leave one animal 

 in the course of a meal if disturbed, to finish feeding on another. 

 For this reason they are of importance in mechanically trans- 

 mitting blood diseases. 



It has been shown that the trypanosome of sleeping sickness, 

 T. gambiense, can be transmitted by interrupted feeding, and a 

 few years ago Macfie showed that the Nigerian strain of the 

 parasite could go through at least part of its development in the 

 gut of the black stable-fly, Siomoxys nigra (see p. 98). 



More serious than this is the relation of stable-flies to anthrax 

 (see p. 488). This fatal disease of domestic animals and man is 

 caused by bacteria which live long enough on or in the proboscis 

 of stable-flies to be readily transmitted by them within an hour 

 or two after an infective feed. The biting flies of this or other 

 species which congregate to feed on sick or dying animals must 

 be looked upon as a serious source of danger. Other diseases, 

 such as foot-and-mouth disease, to which both animals and man 

 are susceptible, may presumably be transmitted in like manner 

 by these flies, though no proof of it has yet appeared. 



In 1912 and 1913 several American workers, among them Dr. 

 M. J. Rosenau, of the U. S. Public Health Service, adduced the 

 theory that the stable-fly, S>tomoxys calcitrans, was responsible 

 for the transmission of infantile paralysis, and the theory was 

 apparently supported by some facts in the epidemiology of the 

 disease (though contradicted by others), and by carefully con- 

 ducted experiments. In subsequent experiments, however, by 

 the same and other workers, the results have been uniformly 

 negative, and in the meantime much data has been collected to 

 show that this terrible disease, which reached unprecedented 

 proportions in New York City and vicinity during the past 3-ear 

 and terrorized the entire United States, is transmitted by con- 

 tagion, and not through the agency of any particular insects. 

 It cannot be said that the disease is never transmitted by biting 

 flies, or by ordinary houseflies, but that insects are not the main 

 or even important factors in the spread of the disease is now a 

 fairly well-established fact. 



Control. — Control of the stable-flies and of allied species of 

 biting flies depends almost entirely on the elimination of their 

 favorite breeding places. In the case of Stomoxys, which is the 



