94 OLD FLIES IN NEW DRESSES 



In this case the circumstances are all in 

 favour of the production of an effect of 

 brilliant colouration ; but going to the other 

 extreme, with a dull light, a dark bottom 

 and cloudy water, we have the dullest- 

 coloured fly accounted for, as the first con- 

 ditions accounted for that which was most 

 gaudy. This also explains the fact that 

 the flies which go in various gradations 

 of colour between these extremes are 

 most suitable for various conditions of the 

 weather, water, and locality. 



In the case of the Salmon-fly, probably 

 the salmon remembers, when he has 

 reached fresh water, many an appetising 

 morsel in the shape of a crustacean or small 

 fish, and takes the fly for one of these. 



In the case of the trout we know that 

 crustaceans are very acceptable to them, 

 and though probably fresh water will not 

 produce the brilliant effect which is pro- 

 duced by salt water as I have described 

 above, still, as fancy Trout-flies do not run 

 to such gaudy colours as do Salmon-flies, 

 still the effect should be sufficient to 

 account for a fair amount of brilliant colour 

 under similar conditions. No doubt some 



