432 THE DISEASES AND DISORDERS OF THE OX. 



herds. We propose to deal with this creature and the gad-fly 

 first, and then we shall proceed to consider other parasites. 



The picture below is takeoj with apologies to Miss Ormerod, 

 from her article above referred to. The bot-fly or warble-fly of 

 the ox {Hypoderma bovis) is about half-an-inch in length, and 

 the general appearance is not unlike that of the bumble-bee. 

 The annual pecuniary loss occasioned by this insect and by the 

 gad-fly of the ox is very great. One of these insects on a hot 

 summer's day is capable of upsetting a whole herd, and it is just 

 possible that they may be the means of transmitting blood dis- 

 eases, as well as of bringing about other well-known damage. 

 About the year 1825, these creatures appeared in large numbers 



Fig. 54. — The Wakble-fly of the Ox, and its Larva. 



in France, causing considerable mischief, fever, and death. They 

 are very generally present in cattle imported from America and 

 other warm countries, and hence any preventive measures should 

 certainly include the destruction of the larvae in oxen brought 

 from abroad, so far as might be found practicable. 



It is in the latter days of May, in June, July, and also in the 

 beginning of August, that the female warble-fly of the ox is 

 busily engaged in laying its eggs on the backs of horned cattle. 

 The oxen are terrified, and, in order to escape their tormentors, 

 will dash madly into the thickest fences. If the ploughman be 

 engaged in ploughing with oxen when the warble-fly and gad-fly 

 are on the war-trail, he will lose all control over his team; 

 and hence on hot and sultry days the ploughing has to be de- 

 ferred until the cool of the evening, when these insects are not 

 on the wing. Having deposited its e^g or eggs, the warble-fly 

 returns to the hedgerows or woods, in order to procure a supply 



