Finn investigated the palatability of a number of Indian insects. He found that most of the birds with which he experimented objected to the Danaine butterflies; but they disliked still more intensely two butterflies belonging to groups not universally protected—a swallowtail (Papilio aristolochiæ) and a white (Delias eucharis).
Finn further experimented with the tree-shrew or Tupaia (Tupaia ellioti), which feeds largely on insects. He found that this creature refused most emphatically all these warningly-coloured butterflies. It would under no circumstances eat the Danainæ, whereas the birds would do so if no more palatable insects were offered to them at the time.
Colonel A. Alcock found that a tame Himalayan bear indignantly refused to eat a locust (Aularches militaris) gaily coloured with black, red, and yellow, and exhaling an unpleasant-smelling froth; but this bear readily devoured ordinary brown or green species.
Among cold-blooded vertebrates the common European salamander, with its bright black and yellow markings, is a striking example of warning colouration; its skin exudes, on pressure, a very poisonous secretion.
Colonel A. Alcock has described a small siluroid sea-fish, brightly banded with black and yellow, and armed with poison spines.
A well-known Indian poisonous snake, the banded Krait (Bungarus cœruleus), is conspicuously barred with wide bands of black and yellow; and in South America there occur numerous species of coral snakes, in which red is added to these conspicuous colours.
The only known poisonous lizard—the Heloderm of Mexico—is conspicuously blotched with black and salmon-colour.
Among birds, no instances of warning colouration have been recorded, though Professor Poulton has suggested that possibly the striking and contrasted tints of many tropical species may be due to this cause. The suggestion is an ingenious one, but is at present totally unsupported by evidence.
The skunks are often cited as an excellent example of warning colouration among mammals. Skunks are most conspicuously arrayed in black and white—the latter above, not below, as is usual—and have bushy tails, which they carry erect. Although less powerful and ferocious than other members of the weasel family, to which they belong, skunks are notoriously protected by their abundant secretion of a very fetid liquid.
For further examples of warning colouration we would refer the reader to Beddard’s illuminating book, entitled Animal Colouration.