56 The Selection Theory 
among those with unpalatable warning colours. Hence the imitation 
of different immune species by Papilio dardanus ! 
I regret that lack of space prevents my bringing forward more 
examples of mimicry and discussing them fully. But from the case 
of Papilio dardanus alone there is much to be learnt which is of the 
highest importance for our understanding of transformations. It 
shows us chiefly what I once called, somewhat strongly perhaps, the 
omnipotence of natural selection in answer to an opponent who had 
spoken of its “inadequacy.” We here see that one and the same 
species is capable of producing four or five different patterns of 
colouring and marking; thus the colouring and marking are not, as 
has often been supposed, a necessary outcome of the specific nature 
of the species, but a true adaptation, which cannot arise as a direct 
effect of climatic conditions, but solely through what I may call the 
sorting out of the variations produced by the species, according to 
their utility. That caterpillars may be either green or brown is 
already something more than could have been expected according 
to the old conception of species, but that one and the same butterfly 
should be now pale yellow, with black; now red with black and 
pure white; now deep black with large, pure white spots; and again 
black with a large ochreous-yellow spot, and many small white and 
yellow spots; that in one sub-species it may be tailed like the ancestral 
form, and in another tailless like its Danaid model,—all this shows a 
far-reaching capacity for variation and adaptation that we could 
never have expected if we did not see the facts before us. How 
it is possible that the primary colour-variations should thus be 
intensified and combined remains a puzzle even now; we are 
reminded of the modern three-colour printing,—perhaps similar 
combinations of the primary colours take place in this case; in 
any case the direction of these primary variations is determined by 
the artist whom we know as natural selection, for there is no 
other conceivable way in which the model could affect the butterfly 
that is becoming more and more like it. The same climate sur- 
rounds all four forms of female; they are subject to the same 
conditions of nutrition. Moreover, Papilio dardanus is by no means 
the only species of butterfly which exhibits different kinds of colour- 
pattern on its wings. Many species of the Asiatic genus Elymnias 
have on the upper surface a very good imitation of an immune 
Euploeine (Danainae), often with a steel-blue ground-colour, while the 
under surface is well concealed when the butterfly is at rest,—thus there 
are two kinds of protective coloration each with a different meaning! 
The same thing may be observed in many non-mimetic butterflies, for 
instance in all our species of Vanessa, in which the under side shows 
a grey-brown or brownish-black protective coloration, but we do 
