BOT-FLIES. 



215 



deeper and deeper into the alveolus that is formed under the 

 influence of the irritation due to these hooks, and the pro- 

 ducts of the inflammation secreted by the small wound in 

 the membrane furnish the food for these maggots or bots. 

 Fig. 176 shows an infested stomach and also the numerous 

 bots (as many as seven hundred have been counted in ex- 



Fig. 177 .— O a tttrophilus larvEc; to the left G. equi; -near middle G. hamor- 

 rhoidalis; to tbe right, G. nasalis; below larvae their last joints from behind. 

 Enlarged. After Brauer 



treme cases), and the little pits produced by them. These 

 bots are, when young, flesh-colored, later they are yellowish- 

 brown. 



The larva, after moulting twice, and changing from a 

 very long and fusiform being into one shaped like those 

 shown in the illustration, at last reaches its full size, which 

 takes place alter having been in the stomach of its host 

 about ten months. It now detatches itself voluntarih^ and 

 passing along with the alimentary matters is finally expelled, 

 and in this way reaches the ground. It is at this period 

 still quite active and is enabled to penetrate the ground to 

 a sHght depth where it gradually becomes rigid and motion- 

 less. After one or two days its old larval skin assumes a 

 bright brown color, which later becomes darker and darker ; 

 the skin hardens and shrinks a little, and gradually assumes 



