THE EOT FLIES 



Although the Family (Estridce, or Bot Flies, is not 

 extensive, it is too important to be overlooked as it 

 includes at least three species which are parasitic upon 

 the horse, ox, and sheep. These are the Horse Bot 

 Fly {Gastrophilus equi). Ox Warble Fly {Hypoderma 

 bovts and Imeatum), and Sheep Nostril Fly {CEstrus ovts). 

 The larva, which is a parasite upon the horse, finds its 

 way into the stomach, those on the backs of oxen are 

 found under the skin, and the one that attacks the placid 

 sheep is discovered around the nostrils of the fleecy- 

 clad animal. 



The Horse Bot somewhat resembles a bee in 

 appearance. It is brownish in colour and hairy, and 

 has a stout body. The larvas feed upon the mem- 

 brane of the horse's stomach, and attach themselves 

 by hooks. As many as a thousand larvae have been 

 found in a single horse. 



The Ox Bot is black, with white hairs on the head, 

 thorax, and tip of abdomen. It also is very hairy. 

 Having no mouth, the adult insect takes no food. It 

 is the larva which does the damage. The mature insect 

 only flies in sunshine, and may then be seen attacking the 

 legs of cattle, whereon the eggs are chiefly laid. The 

 larva is Ucked into the mouth by the beast attacked, 

 but eventually makes its way through the flesh of its 

 host to the back. 



The Sheep Nostril Fly is yellowish-brown, with black 

 and silvery-white hairs on the abdomen. The female 

 may produce either eggs or living larv^, and these 



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