i6o 
is that which may be generically termed defensive colouring.”— 
(.Darwin and After Darwin, p. 316.) 
Mr. Henry Walter Bates was the first to apply the 
theory of Natural Selection to the phenomena of animal 
colouring, in his classical paper entitled “ Contributions 
to an Insect Fauna of the Amazon Valley, Lepidoptera: 
Heliconidaef* he described the manner in which one species 
of butterfly, protected by a nauseous taste, was imitated or 
mimicked by another insect not so protected, and he attri 
buted this strange resemblance to the action of Natural 
Selection. This interpretation was afterwards extended to 
those species which mimic the colour and form of some of 
the objects by which they are ordinarily surrounded. The 
existence of certain very conspicuously coloured insects 
presented an unexpected difficulty ; but Mr. Wallace met 
this objection with an explanation which has been generally 
accepted as a remarkable confirmation of the theory. 
Such is the historical order of the application of Natural 
Selection to the problem of defensive colours. But we 
shall perhaps understand the question better if we realise 
the logical explanation which binds together these different 
phenomena ; for, as Mr. Boulton says : “ in this, as in so 
many other cases, the steps by which the subject is best 
approached are almost exactly opposite to the historical 
steps by which it was gradually understood.”f 
The logical nexus, which binds together all the phe 
nomena of defensive colouring, may be stated thus. At 
the outset, the advocate of Natural Selection, already con 
vinced, as we have seen, that his theory is a great law of 
nature, has no hesitation in assuming that defensive colour 
ing is an illustration of the action of this great principle. 
* The Transactions of the Linnean Society, vol. xxiii., part the third, 
PP- 495-5M- 
t The Colour of Animals, p. 220.