726 DISEASES OF THE SKIN. 



belongs to the genus melophar/ics. It is of a dark reddish colonr, 

 destitute of wings, and is so tenacious of life that it will exist in 

 a fleece twelve months after the animal is shorn. They become 

 numerous in winter, and are best destroyed by an arsenical dip. 



FAMILY OF BOT-FLIES (CESTRIDEA). 



In this division the eggs are deposited in the skin of our 

 patients, and are there developed into the larvae of the fly. 



The female oestrus has a horny ovipositor, which slides out 

 and in, lil^e a telescope, and bears five teeth at the end. On the 

 one hand, it has been asserted that this ovipositor is used as a 

 boring apparatus in burying the eggs at the moment of laying ; 

 on the other, that it has not sufficient strength for this purpose, 

 that the eggs are stuck upon the hairs, and that only the larvse 

 bore under the skin. 



The bot of the ox, (Estrus hovis, is best known in this 

 country, and, according to Mr. Bracy Clark, it is the largest 

 European species of this genus. It is not unfrequently seen in 

 country situations, on the backs of oxen and cows, causing the 

 formation of tumours as large as pullets' eggs on the sides and 

 about the back and loins, which are called by the country 

 people warbles, wornils, wormuls, and sometimes bots. Further,/ 

 Mr. Clark says — " That we may continue the history of thes6 

 flies with some degree of uniformity, we shall commence its 

 operations with some remarks on the deposition of the eggs\ 

 Tliis act appears to be attended with severe suffering, or appre- 

 hension at least, which makes the cattle run wild and furious, 

 and gad and stray from the pastures ; and hence the ancient 

 epithet of gad-fly. When yoked to the plough, the attack 

 of this fly is attended with real danger, since they (the 

 cattle) become perfectly uncontrollable, and will often run 

 directly forwards through the hedges, or whatever obstructs 

 their way. 



" When cattle are attacked by this fly, it is easily known by 

 the extreme terror and agitation of the whole herd. The unfor- 

 tunate object of the attack runs bellowing from among them to 

 some distant part of the heath or nearest water ; the tail, from 

 the severity of the pain, is held with a tremulous motion straight 

 from the body, and the head and neck stretched out to the 

 utmost." 



