234 



DIPTERA OR TRUE FLIES. 



Sheep Nasal-fly (CEstrus ovis), and the Horse-bots (G'asfro^jhilus 

 equi, G. nasalis, &c.), which we will deal with in the above- 

 mentioned order. 



Fig, 129.— Ox->rA]iBi,E Fi.Y 

 (Hypoderma hovit). 



Ox-WARBLES OR BOT-FLT (HtPODBRMA BOVIS AND H. LINEATa). 



These two species, which are very similar in appearance, at 

 one time caused serious loss amongst beasts : the annual amount, 

 according to Miss Ormerod, was something like £7,000,000. 

 But, thanks to her great energies, this 

 serious malady has been checked, although 

 it still does a great amount of harm. The 

 Ox-Warble fly (fig. 129) is like a small 

 hairy humble - bee in appearance, gaily 

 coloured with thick hair of yellow, black, 

 and red bands on the abdomen, and with 

 yellow and black marks on the thorax. The head of these 

 CEstridaa is large, but the mouth is very rudimentary, The 

 Warble-fly itself cannot bite like the Gad-fly ; it pursues the 

 cattle to lay its eggs. The Ox- Warble fly ap- 

 pears in the summer from June to August and 

 September, delighting in hot still days, when 

 we can hear its low dull '' burr " in the air. 

 It is quite a mistake to fancy the \\'arble-flies 

 make no noise. I have frequently heard the 

 low hum produced by CEstriis ovis, and taken 

 the insect on the wing. The ox-pest lays its 

 eggs on the hair of the legs and flanks, and it 

 is these eggs that hatch into the so-called 

 "Ox-bots" (fig. 130). At first the young 

 larvae are white and thread - like. They 

 are sometimes also red when examined in this condition. 

 For some little time they show no signs of their presence 

 externally, but a few months later a small swelling appears 

 over the "hot."' After the larva has moulted a second time 



Fio, ISO.— Ox-BOT. 

 (Enlarged J). 



