PUBLIC HEALTH 21 



following the habits of certain mosquitoes in this respect. 

 The specific cause of phlebotomus fever is not known, but 

 it has been shown to be an invisible virus. At the present 

 time it is impossible to state whether other insects may play 

 a part in its transmission, although such does not seem prob- 

 able. We have at least one species of Phlebotomus in the 

 United States and it is possible that it might act as a vector 

 should the disease be introduced into our country, although 

 it would seem that such a possibility would have been real- 

 ized already if it were likely to occur, for cases of this common 

 European fever must undoubtedly have been imported. 



The common housefly (Musca domestica) is a common 

 agent in the spread of certain infections which are often 

 grouped under the term of fly-borne diseases. Of these it 

 may be urged that, strictly speaking, there are none, at least 

 in the sense of mosquito-borne diseases. The housefly is not 

 known to be wholly responsible for the transmission of any 

 disease and its relative importance in disseminating several 

 infections of man is still a moot question. By some it is 

 strongly urged as the main means of transmission for several 

 enteric diseases in certain communities; by others it is cast 

 aside without reasonable consideration as a sort of entomol- 

 ogist's nightmare. I can not believe that either course is 

 justified; each seems to be based on prejudice due to lack of 

 knowledge, either respecting the fly or relating to other 

 channels of infection. 



The housefly (Fig. 8) is more truly domesticated than any 

 other insect; it lives and flourishes wherever man establishes 

 himself, but does not thrive elsewhere. It has evidently been 

 associated with him from the remotest antiquity, but has by 

 no means failed to adapt itself to changed conditions. It 

 still develops in the animal and vegetable refuse which ac- 

 cumulates about his habitations and still invades his dwell- 

 ings to partake of his food. In short, it is practically ever- 

 present, for its preferred larval food, horse manure, is usually 

 to be found, and, if not, substitutes are available in greater 

 or less abundance. 



