SERVICE AND UTILITY OF FLIES 79 



first a gardener, and then, when expelled from Para- 

 dise, destined to more laboriously cultivate the earth, 

 it may be held to be man's allotted duty not only to 

 wage war against weeds, but likewise to distinguish 

 friends and foes of all kinds, and treat accordingly 

 creatures even of all branches of the animal kingdom, 

 whether insects, reptiles, birds, or mammals, favouring 

 one and exterminating another. This will be to 

 rule the earth and "subdue it " (Genesis i. 28). Neme- 

 sis will inevitably chastise man unless he rectifies the 

 consequences of his own delinquencies, whether they 

 be direct or indirect. The "good service" of the 

 house-fly is comparable with that of the flea, which 

 performs an unwelcomed and indirect "service," 

 inciting the housewife to have well-swept floors and 

 clean bedding. 



The unalloyed good service of insectivorous flies is 

 quite apparent. The details of their life-history and 

 a description of their different characteristics would 

 make an interesting volume, but the limitations of the 

 present work preclude such enlargement of its scope. 



It certainly stands to the credit of the blue-bottle 

 that she is by far our best native scavenger of carrion ; 

 so good, indeed, that none other as an assistant is 

 needed. She may just possibly sometimes convey 

 germs and contaminate food, but she does not so 

 directly assail man. Her larger size makes her easy for 

 exclusion from the domestic food store. So eager and 

 alert is the female in searching for meat, dead animals, 

 and fish, that our other native carrion-feeding flies are 

 at a great disadvantage in the struggle for existence ; 

 so prompt is she in monopolising carrion, that would- 



