INSECTS AND DISEASES 409 



have a pure water supply it is believed by some authorities 

 that flies are the most common cause of transmitting this 

 disease. One estimate states that the annual financial loss 

 in this country due to typhoid fever is over $350,000,000. 

 The fly as one means of spreading this disease is responsible 

 for a portion of this loss. 



Flies and tuberculosis. Flies may also serve as a means 

 of spreading tuberculosis. The sputum of patients contains 

 large numbers of the bacteria that cause this disease. When- 

 ever flies feed upon this sputum, so commonly deposited 

 by careless persons on streets and sidewalks, the bacteria 

 may be carried off and left in milk and on various articles 

 of food. 



Many diseases to which young children are subject are 

 what are known as intestinal diseases, because they affect 

 the intestines. The bacteria which cause these diseases 

 are taken into the system through the food and drink. 

 Flies are a common means of carrying these children's 

 diseases. 



Great as is the harm done by the fly, one fact stands out 

 prominently; the house fly can be controlled and nearly 

 all the sickness and death due to its activities can be pre- 

 vented through the intelligent cooperation of the citizens 

 of any community. That there have been so many pre- 

 ventable deaths due to ignorance and carelessness is a disgrace 

 to our civilization, but on the other hand this very fact gives 

 great hope for the possibilities of the future. In order that 

 we may be able to apply the most effective remedies in the 

 extermination of the fly, it is necessary that we should first 

 understand the essential facts regarding its life history and 



habits. 



2. LIFE HISTORY OF FLY 



The most important breeding place of flies is horse manure. 

 They breed also in human excrement and in almost any 

 decomposing animal or vegetable matter. Examination 



