EVOLUTION OF THE TROUT FLY. 151 



The Blue or Olive Dun is, I believe, the second 

 Dun fly of the Treatise : 'the body of black wool, 

 the wings of the blackest drake, and the jay 

 under the wing and under the tail.' That 

 dressing is not easy to construe, and I suspect 

 the text is corrupt. It is plain that the fly had 

 a black wool body and I think wings from the 

 quill feather of a drake : not the dark mottled 

 feather, usually called dark mallard; for I 

 think (though it is only a matter of opinion) 

 that when the mottled feather, light or dark, 

 is intended, the Treatise uses the word 'mail,' 

 which would be an appropriate word for a body 

 feather. So our fly has a black wool body and 

 clear dark wings of a drake's wing feather : 

 but what is the meaning of jay under the wing 

 and under the tail ? Does it mean a jay hackle 

 run all down the body from wings to tail, and is 

 this hackle the blue feather, or what is it ? It 

 is difiicult to say. Markham, who corrected so 

 many of the ambiguities of the Treatise, saw 

 this difficulty, for he gives a dressing materially 

 different : body of black wool and wings of the 

 dun feathers of a drake's tail. That is plain 

 enough, and both dressings are fairly good, 

 though a little dark even for the Dark Olive. 

 Cotton gives two Blue Duns, one for February 

 and one for March, besides a Great Dun for 

 February, the best fly for the month, giving 

 admirable sport. He is therefore confusing, 

 but as all three are so alike as to be practically 

 indistinguishable, I take the dressing of the 



