DISTRIBUTION OF DISEASE GERMS 



95 



105. How flies carry bacteria. The mouth and feet of the 

 house fly are covered with small, roughish hairs which, when 

 magnified under a lens, show clearly that many bacteria may 

 lodge there as the fly walks upon the refuse which usually 

 forms its food. Some of the bacteria are swallowed by the fly 

 and may later be excreted and deposited at its next lighting 

 place perhaps 



upon some one's 

 food. The trans- 

 mission of bac- 

 teria by the feet 

 of flies is shown 

 in the accom- 

 panying illustra- 

 tion (fig. 52). 



106. Disposal 

 of house flies. 

 House flies may 

 be disposed of if 

 a little attention 

 is given to the 

 matter. If the 

 refuse in which 

 they lay their 

 eggs, and in 

 which the larvse 

 live, is removed, 



no new crops of flies can be produced. Traps may be so 

 arranged as to catch adult flies, after which they may easily be 

 killed. Obviously cooperation is needed to eliminate flies, for 

 so long as any person- in a community supplies the materials 

 for growth of flies, just so long will that community have 

 flies. It is also to be noted that people who will leave refuse 

 exposed so that flies breed in it are likely to be the kind of 

 people who would allow disease bacteria to get into the refuse, 



By permission of Review of Reviews 



FIG. 52. Bacteria carried by a fly 



A plate of agar culture medium over which a fly was 



allowed to walk. Colonies of bacteria have developed 



where the fly touched the culture medium 



