PUBLIC HEALTH 25 



small blood-sucking fly resembling the housefly in size and 

 general color (Fig. 10). On account of its great abundance 

 about horses and cattle it has been termed the stable-fly, 

 although its larva breed mainly in fermenting vegetable 

 material rather than in manure. The adult flies readily bite 

 human beings, particularly in damp weather, and this habit 

 has given rise to the popular idea that houseflies bite before 



FIG. 10. Stable-fly (Stomoxys calcitrans}. 



a shower. The stable-fly is most important as a pest of ani- 

 mals, as it has not been definitely proved to be more than an 

 accidental carrier of any disease affecting man. It was at one 

 time thought to be a carrier of poliomyelitis (infantile paraly- 

 sis), but it now seems probable that such is not the case. 



One of the most important insect-borne human diseases 

 which does not exist in the new world is African sleeping 

 sickness. In recent years this malady has decimated the 

 native population in certain parts of eastern equatorial 

 Africa and any extension of its range would be most serious. 

 It seems very unlikely that America will ever have to face an 

 epidemic, for the introduction of sleeping sickness together 

 with its carriers is not at all probable, and the possibility of 

 its becoming established, even after introduction, is still 



