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"Knowledge" December, 1903. 

 Protective resemblance in Butterflies. 



Sir, 



Mr. Rogers' letter in the September number of " Knowledge" 

 on protective resemblance in butterflies opens up a fairly large 

 question. In a note by Mr. Carpenter I see this resemblance 

 is attributed to natural selection, both with regard to the 

 Brazilian butterflies and the moths which assume a smoke- 

 colour in our own country. 



With regard to the former it would be most interesting to 

 know how long a time was occupied in their becoming like the 

 granite ; but with regard to the effects of the smoke of London 

 and other towns, such moths as betid aria and abrupt aria have 

 certainly got darker in our own time, which hardly coincides 

 w r ith the working of evolution, which is considered so slow as to 

 be almost inperceptible. 



In the Entomological Society's Transactions for 1903 there 

 is an article on the experiments carried out by Prof. E. B. 

 Poulton on the colour-relation between lepidopterous larvae and 

 their surroundings. These exhaustive experiments fully prove 

 that the larvae of O. Bidcntata and G. Qiiercifolia are so extremely 

 sensitive to the colour of their close surroundings that if they be 

 moved from a dark stem to a piece of lichen, for instance, and 

 nothing else be given them to rest on (neither of them rest on 

 their food-plant) they will, like the chameleon, shortly change 

 their pattern from dark to speckled, and assume again a 

 protective colouring. 



May not this colour-sensitiveness in certain individuals be 

 responsible for much that is put down to natural selection, and 

 account for the many glaring failures that occur in the principle 

 of protective colouration ? 



(Signed) Jos. F. Green. 



Royal Societies' Club, 



12th November, 1903. 



