THE BOT- OR WARBLE-FLY 31 



the butcher on a warbled carcass is estimated 

 at 65. Sd. 



Finally there is a loss to the stock-raiser 

 and dairy farmer. We shall have occasion 

 later to refer to the curious psychological 

 effect the warble-fly has upon the cattle, 

 causing them to ' gad ' or stampede in wild 

 gallops, which interferes with fattening, dete- 

 riorates the milk-supply, and is especially 

 injurious to cows with calf. Mr. Imms, in 

 Jiis most useful summary of the warble-fly, 

 tells us that the loss due to H. lineatum in 

 America is calculated at 28 per cent, of their 

 total value of all the cattle in the States. 

 Some authorities place the total loss to 

 the agricultural community in England at 

 £2,000,000, others at £7,000,000, a year, whilst 

 others estimate that the loss amounts to about 

 £1 sterling on every head of horned cattle. 



Curiously enough, the fly itself is rarely 

 seen, and still more rarely taken. Mr. Imms 

 records only two specimens of H. bovis in the 

 collections of the British Museum, and but 

 fifteen of H. lineatum. A similar scarcity 

 of imagos in public collections obtains on the 

 other side of the Atlantic, where for many 

 years the last-named species was alone recog- 

 nised. Two years ago, however. Dr. Hadwen, 

 working in Canada, established the widespread 

 existence of H, bovis in the Dominion : 



