CHAPTER V. 



ON ARTIFICIAL FLIES. 



H ETHER, as stated by Ronalds and 

 other early professors, the different 

 shades of blue, olive, and yellow dun, 

 iron blue, pale evening, and July dun, March and 

 Turkey brown, green drake and dark mackerel, 

 are each distinct and separate varieties, or whether, 

 as asserted by Foster, the blue, olive, and yellow 

 dun, and the other flies enumerated above, are, in 

 fact, the same insects, but slightly altered in tint 

 according to the season, temperature, and other 

 natural causes, is a very difficult point to determine. 

 I am, however, inclined to share the opinion held 

 by Foster, having frequently found in the case of 

 the olive dun, the fry par excellence in the south of 

 England, that even on consecutive days in the 

 spring, with an increase of temperature the colour 

 has become many shades lighter, and more watery 

 in appearance, and on a corresponding decrease of 

 temperature taking place, the fly has hatched of a 

 darker colour and more opaque in texture. 



