Further, Finn found that bulbuls, the commonest garden birds in India, ate the Danainæ readily in captivity, even when other butterflies could be had, which was not the case with most other birds. Bulbuls did, however, usually refuse the Delias and Papilio mentioned above.
The Skunk is preyed upon in America by the Eagle-owl (Bubo virginianus) and the Puma.
Thus, animals provided with natural defences are not immune from attack.
Hence natural selection cannot have encouraged the survival of individuals which displayed a conspicuous colour, for the sake of the “warning.”
We must not forget that many creatures armed with powerful weapons possess the unobtrusive drab, brown, or green colouration which is associated with concealment from foes.
There can be little doubt that, but for the fact that the hive-bee can inflict a sting more severe than that of the wasp, this useful insect would have been cited as a case of a protectively coloured creature. Notwithstanding its sober brown colouring, the hive-bee is recognised and avoided.
Professor Poulton records that the dull inconspicuous caterpillar of the moth (Mænia typica) is rejected by reptiles. It must be admitted, however, that these cases among insects are very rare.
The smooth newt (Molge vulgaris), a relation of the salamander, is protected by a poisonous skin; nevertheless the creature has a dark brown back and spends most of its time on land. Its black-spotted, yellow under-surface may have some protective value in the water. Neither the pike nor the common European water-tortoise will eat this newt.
Toads are nearly all very inconspicuous; nevertheless they are well protected by the acrid secretion from the skin glands; moreover, they are both recognised and avoided by those predacious creatures to whom they are distasteful. Hawks, although as a rule plainly coloured, are certainly recognised by all other birds. It would seem, therefore, that “warning colours,” like the similar striking hues of many domestic animals, are incidental attributes. It has been possible for their owners to develop them, because for the most part let alone.
Eisig, long ago, pointed out that the brightly coloured pigment in the skin of these warningly coloured insects is in certain cases of an excretory nature. Therefore the inference which should be drawn is, as Beddard points out on page 173 of his Animal Colouration, “that the brilliant colours (i.e. the abundant secretion of pigment) have caused the inedibility of the species, rather than that the inedibility has necessitated the production of bright colours as an advertisement.” In other words, Neo-Darwinians put the cart before the horse!