112 THE VALUE OF COLOUR 



original letter exists, 1 and in it we are told that 

 he had taken the advice given by Bates : * You 

 had better ask Wallace.' After some considera- 

 tion Wallace replied that he believed the colours 

 of conspicuous caterpillars and perfect insects 

 were a warning of distastefulness and that such 

 forms would be refused by birds. Dai-win's reply 2 

 is extremely interesting both for its enthusiasm at 

 the brilliancy of the hypothesis and its caution in 

 acceptance without full confirmation : 



' Bates was quite right ; you are the man to apply to in a 

 difficulty. I never heard anything more ingenious than 

 your suggestion, and I hope you may be able to prove it 

 true. That is a splendid fact about the white moths ; * it 

 warms one's very blood to see a theory thus almost proved 

 to be true.' 



Two years later the hypothesis was proved to 

 hold for caterpillars of many kinds by J. Jenner 

 Weir and A. G. Butler, whose observations have 

 since been abundantly confirmed by many natu- 

 ralists. Darwin wrote to Jenner Weir, May 13, 

 1869 : * Your verification of Wallace's suggestion 

 seems to me to amount to quite a discovery.' 4 



RECOGNITION OR EPISEMATIC CHARACTERS 



This principle does not appear to have been 

 in any way foreseen by Darwin, although'he draws 

 special attention to several elements of pattern 



1 Life and Letters, iii 93, 94. z Life and Letters, iii. 94, 95. 



3 A single white moth which was rejected by young turkeys, 

 while other moths were greedily devoured, Natural Selection, 

 1875, 78. 



4 More Letters, ii. 71 (footnote). 



