252 CONTROL OF FLIES 



guiding principle being to attract flies to one spot and catch 

 them. For example, he found that multitudes of flies could be 

 caught in a garbage can. if the cover was held up slightly all 

 round by strips of metal so that flies could easily crawl in, 

 and a hole, covered by a wire trap, made in the lid. The flies 

 entered the can, attracted by the odour, and, attempting to 

 escape by the only opening through which light came, passed into 

 the trap. 



Aleasiires against lafocE. 



If it can be proved beyond doubt that house-flies are 

 important transmitting agents in such serious and widespread 

 diseases as epidemic diarrhea and typhoid fever, the work of 

 limiting their numbers should be undertaken seriously. The facts 

 that they undoubtedly distribute faecal bacteria, and that their 

 presence is evidence of insanitary conditions, are in themselves 

 sufficient justification for urging that the problem should be 

 dealt with. 



" The whole expense of screening should be an unnecessary 

 one, just as the efl'ort to destroy flies in houses should be 

 unnecessary. The breeding should be stopped to such an extent 

 that all these things should be useless" (Howard, 191 1, p. 534). 



" The work of control can be greatly furthered by the 

 individual citizen ; indeed, the California State Board of Health, 

 in Bulletin No. 11 (1909), makes the following statements : 

 * This work can be done only by an united effort. The citizen 

 must do the work, and should do it willingly, but, if negligent, 

 the strong hand of the law should compel it.' The citizen must, 

 however, have instruction in the matter, since there is the greatest 

 ignorance relative to the life history and development of the 

 house-fly and disease transmitting agents in general. The 

 writer finds that this ignorance is as prevalent among the 

 educated as among the uneducated. Few ideas are more firmly 

 rooted in the mind of the average man or woman than that 

 Nature has brought forth nothing that is useless in the economy 

 of the human family.... Some have said that the house-fly acts as 

 a scavenger, and is, therefore, a friend of man. The Iioiisc-fly is 

 the poorest of scavengers, and one of the most dangerous of 



