MELANISM AND MELANOCHROISM IN BRITISH 

 LEPIDOPTERA. 



By J. W. TUTT, F.E.S. 

 {Continued from page 325.) 



Tn The Entomologisf s Record, etc., vol. i., pp. 232, 233, I 

 -'■ referred to a paper by Lord Walsingham, in which it was 

 suggested that the dark coloration of insects was probably due 

 to the rapidity with which these colours absorbed heat in high 

 latitudes and altitudes ; and although I quite admitted in my 

 remarks, that a dark colour would be an advantage, under such 

 conditions, to those insects possessing it, yet, since a dark 

 coloration was not characteristic of high latitudes and alti- 

 tudes, the advantage due to the rapidity of absorption could 

 hardly be looked upon as a cause of melanism. Referring to 

 this in his Presidential Address to the Fellows of the Entomo- 

 logical Society (^tndc Trans. Ent. Sac. Loud., iSgo, pp. liv., Iv.), 

 Lord Walsingham says : — " Mr. Tutt, referring to a paper of 

 my own in which I called attention to the tendency to 

 melanism exhibited by Arctic and Alpine Lepidoptera, points 

 out that insects from high latitudes are not generally melanic. 

 I think I may at once admit that I had used the term * melanic ' 

 somewhat incorrectly in this connection ; what I desired to 

 point out was the general tendency of Arctic Lepidoptera to a 

 certain suffusion of markings, and to an increase in the pro- 

 portion of dull or dingy scales calculated more rapidly to 

 absorb heat than the purer white of more southern varieties. 

 Such a tendency will, I think, be admitted to exist, but I am 

 aware it is far more conspicuous in many insular and Alpine 

 districts ; and, while I cannot agree that the arguments put 

 forward in that paper are in any way undermined by this 

 admission, or that the advantage secured to the species by the 

 development of colour capable of rapidly absorbing heat has 

 been in any way disproved, I am quite willing to accept Mr. 

 Tutt's assertion that melanism does not habitually occur unless 

 lower temperature is accompanied by increased humidity ; 

 qualifying the acceptance only by suggesting that anything 

 which would have the same effect as increased humidity in 

 diminishing the action of sunlight would probably be found to 

 produce the same results." 



I am very pleased that Lord Walsingham thus far admits 

 the justice of my criticism. I quite agree with him that the 



