A Naturalist in Nicaragua

But--and here comes in the principle to which the term "mimicry" is now restricted--if warning colours are helpful to noxious animals, then defenceless animals acquiring these colours will share in the protection afforded by them. And so we find a deceptive similarity between animals occurring in the same district, but not closely related, in which the mimicked form is unpalatable or has an odour repulsive to birds and lizards. It must, of course, be understood that the mimicry is unconscious, the result, as in the cases of cryptic resemblance, having been brought about by natural selection--the less perfect the mimicry the more liable are the individuals to be attacked, and the less chance have they of reproducing their kind. [via]