II 



THE NATURAL ENEMIES OF THE TYPHOID 



FLY 



AS with every other Hving creature, nature makes 

 its own effort to Hmit the abundance of the fly 

 under consideration, and the extraordinary facihty for 

 muhiplication which the fly possesses is in turn the re- 

 sult of the instinctive effort of the organism to main- 

 tain its status in spite of the numerous enemies which 

 confront it. The natural enemies of the house fly be- 

 gin with the acme of the vertebrate series (man him- 

 self) and end with the lower forms of plant life, and we 

 will begin our consideration of these agencies with 

 the latter forms. 



Fungous Diseases 



In the autumn it is a matter of common observation 

 that many flies in houses and on the windows become 

 sluggish and frequently die in such positions. The 

 sluggishness may be accounted for in a measure by the 

 advent of cold weather, and as a matter of fact cold 

 weather frequently drives indoors other species of flies 

 of a more sluggish nature than the house fly. In this 

 way the so-called cluster fly (Pollenia rtidis), a rather 

 sluggish species, which will be referred to in another 

 chapter, is frequently found in houses in the autumn. 



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