194 VERMIN IN THE SKIN. 



thousands of maggots, from eggs deposited by the large 

 blow-fly (musca vomitoria, or sarcophaga carnaria^} This 

 fly, like all other dipterous insects, passes through a com- 

 plete metamorphosis, and its larvae or pupae are white 

 worms without feet, which burrow in any putrescent deposit. 

 The blow-fly has its eyes wide apart, its body covered with 

 hair, its face downy and yellow, its belly of a shining dark 

 coffee colour, and with yellow spots dispersed over it, the 

 thorax grey, with three black stripes. As the maggot comes 

 into existence without being endowed with powers of flight 

 or other means of locomotion, the female deposits its eggs 

 wherever putrescent matters accumulate; and large numbers 

 are found on putrid flesh, on living earthworms, on the 

 putrid sores of men and animals, and in the fleeces of sheep. 

 One species of blow-fly Sarcophaga mortuorum frequents 

 burial-grounds, vaults, &c. The attacks which sheep suffer 

 from depend, no doubt, on the quantity of organic matter, 

 yelk, &c., which the blow-fly finds in the fleece for its larvae 

 to live on. 



It is in the summer season, and especially during sultry 

 weather, and after showers, that the fly is most troublesome 

 amongst sheep. The immediate cause of the fly depositing 

 its eggs is often the dirty condition of the tail and quarters 

 in animals that are suffering from diarrhoea. Amongst rams 

 and other sheep with small horns in their foreheads, when 

 they take to fighting and wound each other, the fly is apt to 

 blow on the sore heads. Eilth and wounds, therefore, ren- 

 der sheep liable to be destroyed by the maggot. 



When the sheep is attacked the wool is seen to be raised 

 over the part injured, and the animal is dull and evidently 

 in pain. Often an animal is seen hiding its head, looking 

 dejected and listless, standing apart from the flock, and soon 

 unable to stand. 



