II 
THE NATURAL ENEMIES OF THE TYPHOID 
FLY 
S with every other living creature, nature makes 
i \ its own effort to limit the abundance of the fly 
under consideration, and the extraordinary facility for 
multiplication 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 rudis), a rather 
sluggish species, which will be referred to in another 
chapter, is frequently found in houses in the autumn. 
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