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with arc—the influence of locality, or of some unknown local causes, in determining the colours of insects, and, to a less extent, of birds; and the way in which certain peculiarities in the distribution of plants may have been brought about by their dependence on insects. The latter part of my address will deal with the present state of our knowledge as to the antiquity and carly history of mankind.
ON SOME RELATIONS OF LIVING THINGS TO THEIR
Of all the external characters of animals, the most beautiful, the most varied, and the most generally attractive are the brilliant colours and strange yet often elegant markings with which so many of them are adorned. Yet of all characters this is the most difficult to bring under the laws of utility or of physical connection. Mr. Darwin-as you are well aware—has shown how wide is the influence of sex on the intensity of coloration ; and he has been led to the conclusion that active or voluntary sexual selection is one of the chief causes, if not the chief cause, of all the variety and beauty of colour we see among the higher animals. This is one of the points on which there is much divergence of opinion even among the supporters of Mr. Darwin, and one as to which I myself differ from him. I have argued, and still believe, that the need of protection is a far more efficient cause of variation of colour than is generally suspected; but there are evidently other causes at work, and one of these seems to be an influence depending strictly on locality, whose nature
we cannot yet understand, but whose effects are everywhere to be seen when carefully searched for.
Although the careful experiments of Sir John Lubbock have shown that insects can distinguish colours—as might have been inferred from the brilliant colours of the flowers which are such an attraction to them—yet we can hardly believe that their appreciation and love of distinctive colours is so refined as to guide and regulate their most powerful instinct—that of reproduction. We are therefore led to seek some other cause for the varied colours that prevail among insects; and as this variety is most conspicuous among butterflies—a group perhaps better known than any other-it offers the best means of studying the subject. The variety of colour and marking among these insects is something marvellous. There are probably about ten thousand different kinds of butterflies now known, and about half of these are so distinct in colour and marking that they can be readily distinguished by this means alone.
Almost every conceivable tint and pattern is represented, and the hues are often of such intense brilliance and purity as can be cqualled by neither birds nor flowers.
Any help to a comprehension of the causes which may have concurred in bringing about so much diversity and beauty must be of value ; and this is my excuse for laying before you the more important cases I have met with of a connection between colour and locality.
The influence of Locality on Colour in Butterflies and Birds.-Our first example is from tropical Africa, where we find two unrelated groups of butterflies belonging to two very distinct families (Nymphalidæ und Papilionidze) characterized by a prevailing blue
green colour not found in any other continent.' Again, we liave a group of African Pieridæ which are white or pale yellow with a marginal row of bead-like black spots; and in the same country one of the Lycanidae (Leptena crastus) is coloured so exactly like these that it was at first described as a species of Pieris. None of these four groups are known to be in any way specially protected, so that the resemblance cannot be due to protective mimicry.
In South America we have far more striking cases; for in the three subfamilies Danainæ, Acraina, and Heliconiinæ, all of which are specially protected, we find identical tints and patterns reproduced, often in the greatest detail, each peculiar type of coloration being characteristic of separate geographical subdivisions of the continent. Nine very distinct genera are implicated in these parallel changes-Lycoren, Ceratinia, Vechavitis, Ithomia, Melincea, Tithorea, Acræa, Heliconius, and Eueides, groups of three or four (or even five) of them appearing together in the same livery in one district, while in an adjoining district most or all of them undergo a simultancous change of coloration or of marking Thus in the genera Ithomia, Mechanitis, and Heliconius we have species with yellow apical spots in Guiana, all represented by allied species with white apical spots in South Brazil. In Mechanitis, Melinæa, and Heliconius, and sometimes in Tithorea, the species of the Southern Andes (Bolivia and Peru) are characterized by an orange and black livery, while those of the Northern Andes (New Granada) are almost always
' Romaleosoma and Euryphene (Nymphalidae), Papilio salmoxis and several species of the Vireus-group (Papilionidae).
orange-yellow and black. Other changes of a like nature, which it would be tedious to enumerate but which are very striking when specimens are examined, occur in species of the same groups inhabiting these same localities, as well as Central America and the Antilles. The resemblance thus produced between widely different insects is sometimes general, but often so close and minute that only a critical examination of structure .can detect the difference between them. Yet this can hardly be truc mimicry, because all are alike protected by the nauseous secretion which renders them unpalatable to birds.
In another series of genera (Catagramma, Callithea, and Agrias) all belonging to the Nymphalidæ, we have the most vivid blue ground, with broad bands of orange, crimson or a different tint of Wue or purple, exactly reproduced in corresponding, yet unrelated species, occurring in the same locality; yet, as none of these groups are known to be specially protected, this can hardly be true mimicry. A few species of two other genera in the same country (Eunica and Siderone) also reproduce the same colours, but with only a general resemblance in the markings. Yet again, in tropical America we have species of Apatura which, sometimes in both sexes, sometimes in the female only, exactly imitate the peculiar markings of another genus (Heterochroa) confined to America : here, again, neither genus is protected, and the similarity must be due to unknown local causes.
But it is among islands that we find some of the most striking examples of the influence of locality on colour, generally in the direction of paler, but sometimes of
clarker and more brilliant hues, and often accompanied by an unusual increase of size. Thus in the Moluccas and New Guinea we have several Papilios (P. cuchenor, P.ormenus, and P. tydeus) distinguished from their allies by a much paler colour, especially in the females which are almost white. Many species of Danais (forming the subgenus Ideopsis) are also very pale. But the most curious are the Euplaas, which in the larger islands are usually of rich dark colours, while in the small islands of Banda, Ké, and Matabello at least three species not nearly related to each other (E. hoppferi, E. curipon, and E. assimiluta) are all broadly banded or suffused with white, their allies in the larger islands being all very much darker. Again, in the genus Diadema, belonging to a distinct family, three species from the small Aru and Ké islands (D. deois, D. hewitsonii, and D. polymena) are all more conspicuously white-marked than their representatives in the larger islands. In the beautiful genus Cethosia, a species from the small island of Waigiou (C. cyrene) is the whitest of the genus. Prothoë is represented by a blue species in the continental island of Java, while those inhabiting the ancient insular groups of the Moluccas and New Guinea are all pale yellow or white. The genus Drusilla, almost confined to these islands, comprises many species which are all very pale; while in the small island of Waigiou is found a very distinct genus, Hyantis, which, though differing completely in the neuration of the wings, has exactly the same pale colours and large ocellated spots as Drusilla.
Equally remarkable is the increase of size in some islands. The small island of Amboina produces larger