MAN AS FOOD FOR ANIMALS 35 



Let US first take up the flies, the most numerous, the most 

 dangerous, and the most cruel of all our animal enemies. 



The screw-worm fly, a rather pretty creature common in 

 tropical America — abundant in some places — and occurring 

 as far north as Canada, lives normally in carcasses, but fre- 

 quently it lays its eggs in sores or cuts or in natural body 

 cavities and the maggots radiate from these in all directions. 

 In man the nose, ears and eyes are most aft'ected. All the 

 larger animals in regions where this fly is common are very 

 liable to infection in scratches or other wounds. This fly is 

 of a most persistent nature and sometimes commits suicide 

 in an effort to reach suitable food for its young. When I was 

 collecting birds in the West Indies I wrapped the skins in 

 sheets of cotton wool. This is suflicient to keep out blow- 

 flies; but the female screw-worm flies will bore their way into 

 the cotton, finally becoming hopelessly entangled and dying 

 almost on the flesh they tried so hard to reach. 



There is a closely allied fly with similar habits in southern 

 Asia, and another, less closely related, in Europe which is 

 especially troublesome in Russia; both of these are said to 

 attack only living animals. Many of the flesh flies occasionally 

 breed in wounds or in natural cavities of the body, and these 

 become a terrible curse to wounded soldiers in times of war 

 when their numbers are vastly increased through breeding in 

 unburied corpses. Those large, dark, hairy, rather slow and 

 clumsy flies which commonly get into houses, and especially 

 into cellars, and the smaller shiny green or coppery flies com- 

 monly seen sunning themselves on garbage cans are among the 

 most pernicious of these. The common large gray dark striped 

 flesh-fly also has this habit. 



The larvae of the human bot-fly, which occurs from Mexico 

 to Argentina and is a true bot-fly, live in swellings which they 

 produce beneath the skin. Their method of entering the host 

 is most remarkable. The female bot-fly captures a large 

 female mosquito or other fly and glues her eggs to the under 

 side of its abdomen. When the fly with the eggs attached 



