NATURAL SELECTION 263 



between other species not so involved. Two suggestions may 

 be made. First, it would be instructive to compare the types 

 of colour-pattern found in genera involved in mimicry with 

 those obtaining in normal genera : it seems possible that in 

 the former a series of striking, sharply contrasting patterns 

 would be found, and in the latter a far more graded series of 

 minutely differentiated patterns. The subject, however, could 

 be dealt with only by an expert lepidopterist. Secondly, we 

 are not claiming that selection could not discriminate between 

 colour-patterns : merely that, as a matter of fact, this has rarely 

 happened in the case of specific difference in pattern. This 

 involves the question considered in the last chapter — viz. 

 how far adaptation and specific divergence have been parallel 

 but quite distinct processes. 



Summary of the Examination of the Mimicry Theory 



In the preceding pages we have dealt very briefly with 

 what appear to us to be the main difficulties in the employ- 

 ment of the mimicry theory as important evidence in favour of 

 Natural Selection. In the past some of the criticism of the 

 selective theory of mimicry has been misinformed, but it 

 seemed more necessary for us to point out what considerable 

 gaps there are in our knowledge than to enumerate a long 

 series of cases favourable to the theory. It appeared to us 

 essential to distinguish between what we know and what we 

 infer or guess. 



There is no difficulty in accepting the fact that numerous 

 unrelated animals resemble one another closely in colour. 

 There is a considerable body of evidence favouring the view 

 that brightly coloured animals (especially insects) tend to be 

 distasteful, and vice versa ; there are, however, probably 

 sufficiently numerous exceptions to make extensive generalisa- 

 tions dangerous until more observations have accumulated. 

 On this point systematic examination of a whole local fauna is 

 more important than casual notes. There is a considerable 

 difficulty in explaining the early stages of the evolution of 

 distastefulness and warning colours by the aid of selection, but 

 our knowledge is still too scanty to allow us to do more than 

 note the existence of the problem. 



The existence of conspicuous distasteful forms is the a priori 



