RELATION TO OTHER ANIMALS 



177 



to species of Dermatohia. So far as I am aware no 

 species has been demonstrated that is confined to 

 human beings. 



Almost any part of the animal body may be at- 

 tacked by bots; but in a general way they are most 

 likely to appear in regions which the host is least able 

 to reach with its teeth, e.g., the neck; but they occur 

 often enough in other portions of the body. Occa- 



FiG. 79. — The sheep bot, CEstrus ovis: i. 2, flies; 3, pupa; 4, 5, full-grown 

 larvae; 6, young larva. 



sionally they appear to attack specific organs as those 

 that destroy the testes of squirrels and chipmunks, or to 

 be confined to special regions like those that are so often 

 found around the anal openings of hares and rabbits. 



Some species have almost identically the habits that 

 were observed in the screw-worms entering the head 

 of man through the nostrils. An example of this is 

 the well-known sheep bot, the adult of which lays its 

 eggs ready to hatch or just hatched on the mucus of 

 the nostrils of the sheep. The larvae work their way up 

 into the head passages, feeding on the mucus, on the 

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