234 THE COLOURATION OF INSECTS 



these two is a series of pairs, model uppermost, showing 

 every grade of relationship. 



Mimicry, looked at from one point of view, is merely 

 an example of resemblance to an especial part of the 

 environment, and is strictly analogous to special pro- 

 cryptic resemblance. Both are forms of Apatetic coloura- 

 tion. ^ In one case the insect is like a leaf or twig which 

 is of no interest to an insectivorous enemy ; in the other 

 it resembles another species which the enemy rarely 

 eats, knowing it to be distasteful. There seems no logical 

 reason for supposing that the latter example is beyond 

 the power of natural selection any more than the former, 

 yet in spite of much recent work on these lines by the 

 Hope Department, and also by naturalists in the field, 

 it is held by some that the resemblances are fortuitous, 

 or the result of causes which together or separately are 

 not able to explain facts as are the Batesian and Mullerian 

 theories, based on natural selection. 



An objection is sometimes urged somewhat as follows. 

 Since the potential numbers of patterns are limited, and 

 the number of species large, it is quite possible that the 

 same pattern may have been accidentally produced in 

 two species without there being any meaning to be attached 

 to the resemblance, except mere coincidence. 



Dr. F. A. Dixey dealt with this argument at the 

 meeting of the British Association at Birmingham in 

 1913.2 He showed a number of examples of Lepidoptera 

 from different continents with approximately the same 

 colouration and pattern, and to these cases it would 

 of course be absurd to ascribe a mimetic significance. 

 But it is important to note that such coincidence has 

 gone no further than to produce the crudest of patterns 

 and contrasts, such as a light subapical bar on a dark 

 fore wing, and the likeness even then is not so close as 



^ Colours of Animals. See classification at end. 

 * See Report, p. 618. 



