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- 

fea bi oa WF ieee Gastrophilus larve; to the left G. equi; near middle G. hemor- 
rhoidalis; to the right, G. nasalis; below larve 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 after having been in the stomach of its host 
about ten months. It now detatches itself voluntarily, and 
passing along withthe alimentary matters is finally expelled, 
andin this way reaches the ground. It 1s at this period 
still quite active and is enabled to penetrate the ground to 
a slight 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 
