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VETEEINAEY HYGIENE 



the larvffi are found to occupy, the Cuticola, Gastricola and 

 Caricola, of which the Ox Warble, Horse Bot and Sheep 

 Nostril flies are examples. The object with which all bot 

 flies attack animals is to deposit their eggs or larviE only. 

 The adults have their mouth parts prac- 

 tically abortive. 



Hypoderma bovis, Ox ivarhle or Bot Fly 

 (Fig. 180), is one of the most severe 

 insect pests to cattle living in the open. 

 ■r -v The fly by its presence is said to alarm 



Fig. iso.-Hypoderma gattle, and causes them to gallop wildly 



oovis ; natural size. ' , , 



about, so much so that cows may even 

 bruise their udders in their panic. The flight of the fly 

 is rapid, it hovers over the cattle, then suddenly drops 

 and deposits an egg on the back, rises again and repeats 

 the manoeuvre. The egg is now fixed to the hair, and 

 hatches in the open into a maggot, which then proceeds to 

 make a hole for itself in the skin. It lies beneath the skin 

 during the autumn and winter, during which time it 

 moults, grows, and changes its appearance and colour. 



In the spring a tumour forms, which has an opening in 

 the centre, leading down to the ' warble cell.' Through 

 this opening the maggot when full grown (Fig. 181) squeezes 

 its way, and falls to the ground, where it be- 

 comes a pupa and finally the fly emerges. 



It has now been shown, in the case of 

 H. lineata, the common American species of 

 Warble fly, that the embryo is licked off the 

 skin, and being taken into the mouth it fixes 

 to the throat and then bores its way to below 

 the skin of the back where the Warble is 

 formed. It is possible that this will also be 

 proved for H. bovis. 



The fly is about i inch long, with yellow hairs on the 

 face, yellow and black hairs on the thorax, while those on 

 the abdomen are yellowish white in front, black in the 

 middle, and yellowish-red posteriorly. 



The maggots do considerable damage to animals from 

 the irritation set up in them, while they ruin the hide 

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Fig. 181. — 

 Larva of Hy- 

 poderma bovis. 



