174 ANIMAL PARASITES AND MESSMATES. 



A species, peculiar to the horse in Europe, usually 

 lives in its stomach in summer ; and when its develop- 

 ment is complete, the winged insect follows the course of 

 the food, and goes out from the anus to breathe the open 

 air. The mother fly, excited by the sentiment of maternity, 

 flies round the breast of the first horse that she meets, 

 and lays her eggs there on some hairs which are not 

 beyond reach of the animal's tongue. The horse wishing 

 to get rid of these foreign bodies, hcks them off, and thus 

 they are introduced into the mouth, and from the tongue 

 pass to the stomach. These eggs are hatched in the 

 midst of the gastric juice, the larvae leave them, and 

 the young gadflies find in the juices of the stomach the 

 milk which serves to nourish them. These larvae pass 

 through their metamorphoses in the stomach, and when 

 the young fly has assumed its perfect form, with its 

 delicate wings, its sucker, and its facetted eyes, it leaves 

 the stomach, follows the path traced by the food, arrives 

 some fine day at the rectum, presents itself at the 

 place of exit, and takes its flight. Thus the fly can 

 take its journey through the intestines on a portion of 

 the digested food. 



When she has once taken her flight she is very near 

 the end of her life, and after a moment of love she gives 

 up her place to others. 



There is another gadfly which finds a creche in the 

 sheep ; but instead of lodging in its stomach, it instals 

 itself in the nostrils, which are more easily reached. This 

 second species goes through its evolutions in the vestibule. 



This is the species which sometimes introduces itself 

 into the body of man. Many instances of this have been 

 known, and our late colleague Spring gave a very in- 



