224 THE COLOURS OE ANIMALS 



Convenience of the term Mimicry 



Mr. Bates's term has been criticised because it is 

 generally used to describe voluntary actions, whereas 

 the Mimicry alluded to in these pages is of course un- 

 conscious, and has been gradually produced by the 

 operation of natural selection. 1 This use of the word 



more, the alleged contrast frequently breaks down ; thus, a dead leaf 

 driven by the wind (see p. 56), or a piece of stick swinging by a thread, 

 are not uncommonly resembled ; while the conspicuous appearance of 

 Mimetic and Warning Colours are most certainly of value during rest 

 as well as during flight (see pp. 189-95). Against the evidence offered 

 by Skertchly (b) may be put the observations of other naturalists 

 (see pp. 228-30; many other examples might have been recorded). We 

 must also remember that very little of the destruction of life which 

 we know takes place is actually witnessed by us. Against (c) may 

 be urged the fact that characters begin to decline directly they be- 

 come useless, while certain mimetic resemblances are perhaps more 

 wonderfully elaborate and perfect than anything else in the animal 

 kingdom. Every naturalist will agree with (d), but it is really de- 

 structive of the argument based upon it. The danger to most 

 mimetic species must indeed be great if measured by the efforts taken 

 to avoid it. Some of the marvellous results of such ' efforts ' are de- 

 scribed in this volume. Skertchly's argument only applies to the 

 numerical ratio between the examples of Mimicry and Protective 

 Resemblance ; and this ratio is readily explicable on other grounds. It 

 has been shown that Warning Colours can only be adopted safely by a 

 small proportion of the insect fauna in any country (see pp. 178-80), 

 and also that mimetic individuals must be far rarer than the nauseous 

 forms they resemble (see pp. 243-44 ; see also p. 231). 



1 After this sentence had been printed I came across a most 

 extraordinary statement of the theory of Mimicry by Skertchly, I.e. 

 This theory ' presupposes (a) that danger is universal ; (b) that some 

 butterflies escape danger by secreting a nauseous fluid ; (c) that other 

 butterflies noticed this immunity ; (d) that they copied it.' The opinions 

 expressed in the words I have italicised will hardly be accepted by a 



