THE HORSE GAD-FLY. 4I3 



inained on the hairs four or five days they become 

 ripe, after which the slightest application of warmth 

 and moisture is sufficient to bring them into life. 

 If at this time the tongue of the horse touches the 

 e^gg, its lid is thrown open, and a small active worm 

 is produced, which readily adheres to the surface of 

 the tongue, and is from thence conveyed with the 

 food to the s'tomach. 



It is however fortunate for the horses that this 

 insect is exposed to so many hazards that scarcely 

 one in a hundred arrives at the perfect state of a fly. 

 The eggs, when ripe, often hatch of themselves, and 

 the larvae crawl about till they die ; others are wash- 

 ed off by the water. When in the mouth of the 

 animal, they have to undergo the ordeal of the 

 teeth and mastication ; and many pass entirely 

 through the intestines with the food. When the 

 larvae arrive at tull growth, and are voided along 

 with the dung, many are either dropped into mud 

 or water, others are crushed to death by being trod 

 upon, and others are picked up by the birds. The 

 perflect fly is very tender, and but ill sustains the 

 changes of weather ; and cold and moisture, in any 

 considerable degree, are probably often fatal to it. 



This Gad-fly is distinguished from the rest of its 

 tribe by having a black band in the middle, and two 

 dots at the tip of its whitish wings. The abdomen 

 is yellow brown, with black spots at the divisions of 

 the segments. The female is more brown than the 

 male, and has her abdomen elongated with a cleft 

 terminal style*. 



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* Linn. Tran. Hi. 2i;8. tab. 23* 



