So far we have only considered the origin of animal colours in general. Mr. Wallace, however, has not only made clear the general connection between beautiful and vivid colours and health, but, by utilising his own researches and those of Mr. Bates and other naturalists, he has been able to show to what a great extent we can explain even the particular colours of the various classes of animals. He distinguishes four classes of animal colours—Protective, Warning, Sexual, and Typical.
(1) Protective Colours.—These “are exceedingly prevalent in nature, comprising those of all the white arctic animals, the sandy-coloured desert forms, and the green birds and insects of tropical forests. It also comprises thousands of cases of special resemblance—of birds to the surroundings of their nests, and especially of insects to the bark, leaves, flowers, or soil on or amid which they dwell. Mammalia, fishes, and reptiles, as well as mollusca, present similar phenomena; and the more the habits of animals are investigated, the more numerous are found to be the cases in which their colours tend to conceal them, either from their enemies or from the creatures they prey upon.”
(2) Warning Colours.—In this class, on the other hand, the object is not to conceal the animal, but to make it conspicuous. Certain species of gorgeously-coloured butterflies, e.g. are never eaten by birds, spiders, lizards, or monkeys, who eagerly feed on other butterflies. “The reason simply is that they are not fit to eat, their juices having a powerful odour and taste that is absolutely disgusting to all these animals. Now we see the reason of their showy colours and slow flight. It is good for them to be seen and recognised, for then they are never molested; but if they did not differ in form and colouring from other butterflies, or if they flew so quickly that their peculiarities could not be easily noticed, they would be captured, and though not eaten, would be maimed or killed.”
Mimicry is the name given to a second and still more marvellous class of Warning Colours. They belong to defenceless creatures which so closely resemble other brightly-coloured but nauseous or dangerous animals that they are mistaken for the latter, and therefore left alone. E.G. “Wasps are imitated by moths, and ants by beetles; and even poisonous snakes are mimicked by harmless snakes, and dangerous hawks by defenceless cuckoos.”
(3) Typically-coloured animals are those species which are brilliantly coloured in both sexes, “and for whose particular colours we can assign no function or use.” This group “comprises an immense number of showy birds, such as Kingfishers, Barbets, Toucans, Lories, Tits, and Starlings; among insects most of the largest and handsomest butterflies,” etc. “It is a suggestive fact that all the brightly-coloured birds mentioned above build in holes or form covered nests, so that the females do not need that protection during the breeding season which I believe to be one of the chief causes of the dull colour of female birds when their partners are gaily coloured.”
(4) Sexual Colours, comprising those cases in which the sexes differ, and with which Darwin’s theory of Sexual Selection is directly concerned. Through no direct fault of his own, Darwin leaves on his readers the impression—which has become almost a commonplace of conversation—that it is the general rule among animals for the males of each species to be more ornamented than the females. The truth is, however, that “with the exception of butterflies, the sexes are almost alike in the great majority of insects. The same is the case in mammals and reptiles; while the chief departure from the rule occurs in birds, though even here in very many cases the law of sexual likeness prevails.”
The reason why I have devoted so much space to Mr. Wallace’s colour theories is to emphasise the truth contained in this last sentence; the fact, namely, that even if Sexual Selection were accepted as an active principle, it would account in only a very limited number of cases for the personal beauty of animals, and the reader of Mr. Wallace’s Tropical Nature and his Contributions to the Theory of Natural Selection cannot fail to be convinced that Sexual Selection does not even hold good in this limited number of cases, but that “the primary cause of sexual diversity of colour is the need of protection, repressing in the female those bright colours which are normally produced in both sexes by general laws.”
Incidentally Mr. Wallace mentions as an additional function of colour the fact that it may serve as a means of recognition to the sexes. “This view affords us an explanation of the curious fact that among butterflies the females of closely-allied species in the same locality sometimes differ considerably, while the males are much alike; for, as the males are the swiftest, and by far the highest flyers, and seek out the females, it would evidently be advantageous for them to be able to recognise their true partners at some distance off.”
To me it seems that this function of colour is, next to Protection, its most important object, and that Mr. Wallace does not give it sufficient prominence. He says, in speaking of Typical Colours, that we can assign “no function or use for them.” But why should they not serve the sexes as a means of recognition at at a distance? especially as colours can be recognised at a greater distance than forms. Many years before Darwin and Mr. Wallace wrote on this subject, Schopenhauer’s genius anticipated this view of the matter. “The extremely varied and vivid colours of the feathers of tropical birds,” he wrote, “have been explained in a very general way, with reference to their efficient cause, as due to the strong effect of the tropical light. As their final cause I would suggest that these brilliant plumes are the gala uniforms by means of which the species, which are so numerous there and often belonging to the same genus, recognise each other; so that every male finds his female. The same is true of the butterflies of different zones and latitudes” (Welt als Wille u. V., ii. 381).
Schopenhauer of course errs in attributing, in his ignorance of Protective, Warning, and other colours, all the hues of birds and butterflies to this agency. But it is probable that whenever colours and other ornaments do not serve for purposes of protection (as e.g. the lion’s mane and the horns of beetles, vide Tropical Nature, p. 202), they serve the purpose of sexual recognition of species. A case cited by Darwin to prove that quadrupeds take notice of colour, is very suggestive in this connection: “A female zebra would not admit the addresses of a male ass until he was painted so as to resemble a zebra, and then, as John Hunter remarks, she received him very readily.”
It is probable, therefore, that in many cases the unique spots and stripes and colours of animals subserve the special use of facilitating the finding of a partner; and in this way they relate directly to the courtship and Romantic Love of animals. Thus we see how the Love affairs of animals may indirectly affect their Personal Beauty in a way quite different from that suggested by Darwin.
LOVE-CHARMS AND LOVE-CALLS
The same reasoning applies to the music of animals, vocal and instrumental, on which Darwin lays great stress. In his opinion, the music of some male animals serves to charm the females æsthetically, and thus gives to the best musicians special advantages through Sexual Selection. But the instances cited by him hardly warrant this conclusion, and seem rather to point to the inference that the function of animal music is chiefly to facilitate courtship, by making it easy for the females to discover the whereabouts of a male of the same species. The evidence tends to show that it is not the male whose voice is most mellow and melodious that catches the female, but rather the one who is most vigorous and persistent and has the loudest organ. As Jaques says in As You Like It: “Sing it: ’tis no matter how it be in tune, so it make noise enough!”