MIMICRY INDEPENDENT OF AFFINITY 233 



these resemblances ; and one of the rare cases in which 

 Darwin's insight into a biological problem did not lead 

 him right was when he suggested that a former closer 

 relationship may help us to a general understanding of 

 the origin of mimicry. 1 The preservation of an original 

 likeness due to affinity undoubtedly explains certain cases 

 of Mimicry, but we cannot appeal to this principle in the 

 most remarkable instances. Further confirmation of this 

 independence of affinity will be found in the additional 

 details supplied in the succeeding Section. 



When we look at the phenomena of Mimicry and 

 Common Warning Colours as a whole, it is found that 

 the theory of Natural Selection is equally applicable 

 throughout ; while the theories of External Causes and 

 Internal Causes cannot be applied to some of the most 

 striking resemblances, those of moths, beetles, and flies 

 to the stinging Hymenoptera. The theory of Sexual 

 Selection is less logically assailable on these grounds ; 

 but with the other two suggested substitutes for Natural 

 Selection, it entirely fails to account for the attractive 

 force exercised by specially protected forms. Under any 

 of these three theories it is a mere coincidence that the 

 insects which are resembled by species of all kinds happen 

 to possess stings — that the central types in the groups 

 of butterflies belong to Sub-Families which are more 

 abundant and even more unpalatable than the generality 

 of their Order. It is, furthermore, a mere coincidence 

 that such groups are formed round the Danainae and 

 Acraeinae, wherever they occur in all the warmer regions 

 of the world, and in tropical America also round the 

 Ithomiinae {Neotropinae), which are closely related to the 

 former, and the Heliconinae, which are closely related to 

 the latter. 



1 See Darwin's letter to Meldola, dated Jan. 23, 1872 ; Poulton, Charles 

 Darwin and the Theory of Natural Selection, London, 1896, pp. 201-2 : also 

 Charles Darwin, The Descent of Man, &c., 10th ed., London, 1874, p. 324. 

 The passage runs as follows: — 'As some writers have felt much difficulty 

 in understanding how the first step in the process of mimicry could have 

 been effected through natural selection, it may be well to remark that the 

 process probably commenced long ago between forms not widely dissimilar 

 in colour.' See also Origin of Species, 6th ed., p. 377. 



