88 



INSECTS AND HUMAN WELFARE 



in recognition of its then, well-known habits. The housefly is 

 probably a native of India from whence it has followed man 

 to the most remote regions of the world. It invariably occurs 

 where human communities become established, but it is so 

 wedded to human society that it is never to be found else- 

 where. Originally a native of the tropics it can successfully 



FIG. 38. A housefly killed by a parasitic fungus (Ernpusa muscae). 

 This fungus, which destroys countless flies, is very generally prevalent 

 during the autumn months. 



overwinter in cold regions under the conditions brought 

 about by civilization, for it finds places of sufficient warmth 

 to enable it to withstand the rigorous winters of very cold 

 climates. In cool regions it is never abundant in the spring, 

 but due to its rapid development becomes increasingly nu- 

 merous as the season progresses, again to disappear rapidly 

 in the autumn (Fig. 38). On account of its importance to 

 public health, the habits of the housefly have already been 

 considered elsewhere. 



Many of us are familiar with the old saying that houseflies 

 bite before a storm. Although responsible for many things, 

 the housefly cannot bite, but the stable-fly (Stomoxys calci- 

 trans), a related fly of similar size and color, with a sharp 



