[37] Euplœa andamanensis, Cethosia biblis, Cyrestis cocles.
In Madagascar we have the very large and singularly white-spotted Papilio antenor; while species of three other genera[38] are very white or conspicuous as compared with their continental allies.
[38] Danais nossima, Melanitis massoura, Diadema dexithea.
Passing to the West-Indian Islands and Central America (which latter country has formed a group of islands in very recent times) we have similar indications. One of the largest of the Papilios inhabits Jamaica,[39] while another, the largest of its group, is found in Mexico.[40] Cuba has two of the same genus whose colours are of surpassing brilliancy;[41] while the fine genus Clothilda—confined to the Antilles and Central America—is remarkable for its rich and showy colouring.
[39] Papilio homerus.
[40] P. daunus.
[41] P. gundlachianus, P. villiersi.
Persons who are not acquainted with the important structural differences that distinguish these various genera of butterflies can hardly realize the importance and the significance of such facts as I have now detailed. It may be well, therefore, to illustrate them by supposing parallel cases to occur among the Mammalia. We might have, for example, in Africa, the gnus, the elands, and the buffaloes, all coloured and marked like zebras, stripe for stripe over the whole body exactly corresponding. So the hares, marmots, and squirrels of Europe might be all red with black feet, while the corresponding species of Central Asia were all yellow with black heads. In North America we might have raccoons, squirrels, and opossums, in particoloured livery of white and black, so as exactly to resemble the skunk of the same country; while in South America they might be black with a yellow throat-patch, so as to resemble with equal closeness the tayra of the Brazilian forests. Were such resemblances to occur in anything like the number and with the wonderful accuracy of imitation met with among the Lepidoptera, they would certainly attract universal attention among naturalists, and would lead to the exhaustive study of the influence of local causes in producing such startling results.
One somewhat similar case does indeed occur among the Mammalia, two singular African animals, the Aard-wolf (Proteles) and the hyæna-dog (Lycaon), both strikingly resembling hyænas in their general form as well as in their spotted markings. Belonging as they all do to the Carnivora, though to three distinct families, it seems quite an analogous case to those we have imagined; but as the Aard-wolf and the hyæna-dog are both weak animals compared with the hyæna, the resemblance may be useful, and in that case would come under the head of mimicry. This seems the more probable because, as a rule, the colours of the Mammalia are protective, and are too little varied to allow of the influence of local causes producing any well-marked effects.
When we come to birds, however, the case is different; for although they do not exhibit such distinct marks of the influence of locality as do butterflies—probably because the causes which determine colour are in their case more complex—yet there are distinct indications of some effect of the kind, and we must devote some little time to their consideration.