DIPTERA. 
73 
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 pass 
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 (Hypoderrna 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 
o o 
beneath, where in 
course of development 
they give rise to the 
large tumours known 
as warbles, each of 
which opens to 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 If. lineatum. It can be easily under¬ 
stood from the fact that since no fewer than four hundred maggots, each grow¬ 
ing to an inch in length, have been known to infest a single beast, the loss 
occasioned by the attacks of this fly is considerable. It has been estimated, 
indeed by Stratton, that in the United Kingdom alone a loss 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 (CEstrus ovis ) lays its eggs 
in the nostrils of sheep, and the maggots after being hatched pass up the nasal 
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 eight at 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 
exterior by means of 
a small aperture. In 
these tumours the 
a be 
OX WARBLE-FLY AND ITS DEVELOPMENT. 
a, Fly; b, Larva ; c, Pupa—the latter from the lower side. (All enlarged.) 
