Alfred Russel Wallace 



as they have yet gone, confirm in every instance my hypo- 

 thetical explanation of the colours of caterpillars. He finds 

 that all nocturnal-feeding obscure-coloured caterpillars, all 

 green and trown and mimicking caterpillars, are greedily 

 eaten by almost every insectivorous bird. On the other 

 hand, every gaily coloured, spotted or banded species, 

 which never conceal themselves, and all spiny and hairy 

 kinds, are invariably rejected y either without or after trial. 

 He has also come to the curious and rather unexpected 

 conclusion, that hairy and spiny caterpillars are not pro- 

 tected by their hairs, but by their nauseous taste, the 

 hairs being merely an external mark of their uneatable- 

 ness, like the gay colours of others. He deduces this from 

 two kinds of facts : (1) that very young caterpillars before 

 the hairs are developed are equally rejected, and (2) that 

 in many cases the smooth pupae and even the perfect insects 

 of the same species are equally rejected. 



His fact^, it is true, are at present not very numerous, 

 but they all point one way. They seem to me to lend an 

 immense support to my view of the great importance of 

 protection in determining colour, for it has not only pre- 

 vented the eatable species from ever acquiring bright 

 colours, spots, or markings injurious to them, but it has 

 also conferred on all the nauseous species distinguishing 

 marks to render their uneatableness more protective to 

 them than it would otherwise be. When you have read 

 my book I shall be glad of any hints for corrections if 

 it comes to another edition. I was horrified myself by 

 coming accidentally on several verbal inelegancies after 

 all my trouble in correcting, and I have no doubt there are 

 many more important errors. — Believe me, dear Darwin, 

 yours very truly, Alfred R. Wallace. 



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