In the Andaman Islands in the Bay of Bengal there are a considerable number of peculiar species of butterflies differing slightly from those on the continent, and generally in the direction of paler or more conspicuous colouring. Thus two species of Papilio which on the continent have the tails black, in their Andaman representatives have them either red or white-tipped.[35] Another species[36] is richly blue-banded where its allies are black; while three species of distinct genera of Nymphalidæ[37] all differ from their allies on the continent in being of excessively pale colours as well as of somewhat larger size. [35] _Papilio rhodifer_ (near _P. doubledayi_), and _Papilio charicles_ (near _P. memnon_). [36] _Papilio mayo._ [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.