DIPTERA. 



73 



OX TYARBLE-FLY AND ITS DEVELOPMENT. 



«, Fly ; b, Larva ; c, Pupa — the latter from the lower side. (All enlarged.) 



oesophagus, making little excavations, and nourishing themselves by sucking up 

 the secreted mucus. Here in perfect security they live and grow for about 

 a year; after which, when nearly full grown, they enter the intestine and p 

 out of the body with the excrement. Falling to the ground, the maggots bury 

 themselves in the soil and enter upon the pupal stage. In favourable weather 

 the perfect insect is produced from the pupa in about six weeks. The ox-bot, 

 or ox-warble (Hypoderma bovis) deposits its eggs in the hair of the skin of 

 cattle, and the mag- 

 gots after hatching 

 burrow through the 

 skin and take up their 

 lodging in the tissues 

 beneath, where in 

 course of development 

 they give rise to the 

 large tumours known 

 as warbles, each of 

 which opens to the 

 exterior by means of 

 a small aperture. In 

 these tumours the 

 maggots remain for 

 ten or eleven months until practically full grown, when, quitting their host, they 

 fall to the ground, bury themselves, and in the course of a month or six weeks 

 emerge from the pupa stage as fully developed flies. The species most commonly 

 met with in England is not H. bovis but H. lineatum. It can be easily under- 

 stood from the fact that since no fewer than four hundred maggots, each grow- 

 ing 1 to an inch in length, have been known to infest a single beast, t lie loss 

 occasioned by the attacks of this fly is considerable. It has hern estimated, 

 indeed by Stratton, that in the United Kingdom alone a less of .something like 

 £8,000,000 per annum is sustained. The mischief begins in the summer, when 

 the cattle gallop about in terror in their vain efforts to escape the flies seeking 

 to deposit their eggs upon them. This causes waste of milk and damage to 

 health. Then there is the damage to the meat by the destruction of the tissue 

 just under the hide, resulting in what butcher's call licked meat or jelly. And 

 lastly, there is the evidence of tanners as to the damage to hides; one estimate 

 given by a firm putting the loss on hides sold at two markets in Birmingham 

 during seven weeks at £545 ; while a Nottingham authority reckons the loss in that 

 town at £1500 to £2000 per annum. The sheep bot-fly ( (Estrus ovis) lays its 

 in the nostrils of sheep, and the maggots after being hatched pass up the naval 

 passages and enter the chamber in the bones of the forehead, where they nourish 

 themselves on the mucus to which the irritation of their presence gives rise. 

 The presence of these parasites, which are seldom fewer than seven or eigW al a 

 time, is most injurious to the infested animal, and gives rise to a sickness of a very 

 serious nature. At the end of about nine months the larvae reach maturity, and 

 making their way again into the nostrils are expelled by the sneezing of their 



