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and splendid colours were considered by all the older writers to be the princes of the whole lepidopterous order. They are usually known by the English term “Swallowtailed butterflies,” because the only British species, as well as a great many of the tropical forms, have the hind wings tailed. They are pretty uniformly distributed over all the warmer regions, but are especially abundant in the tropical forests, of which they form one of the greatest ornaments. In coloration they are wonderfully varied. The ground colour is very frequently black, on which appear bands, spots, or large patches of brilliant colours—pale or golden yellow, rich crimsons or gorgeous metallic blues and greens, which colours sometimes spread over nearly the whole wing surface. Some are thickly speckled with golden green dots and adorned with large patches of intense metallic green or azure blue, others are simply black and white in a great variety of patterns many very striking and beautiful, while others again have crimson or golden patches, which when viewed at certain angles change to quite different opalescent hues, unsurpassed by the rarest gems. But it is not this grand development of size and colour that constitutes the attraction of these insects to the student of evolution, but the fact that they exhibit, in a remarkable degree, almost every kind of variation, as well as some of the most beautiful examples of polymorphism and of mimicry. Besides these features, the family presents us with examples of differences of size, form, and colour, characteristic of certain localities, which are among the most singular and mysterious phenomena known to naturalists. A short statement of the nature of these phenomena will be useful to show the great interest of the subject. In all parts of the world there are certain insects which, from a disagreeable smell or taste, are rarely attacked or devoured by enemies. Such groups are said to be “protected,” and they almost always have distinctive and conspicuous colours. In the Malay Archipelago there are several groups of butterflies which have this kind of protection; and one group is coloured black, with rich blue glosses and VOL. I. 2 ID

ornamented with white bands or spots. These are excessively abundant, and, having few enemies, they fly slowly. Now there are also several different kinds of papilios, which in colour are so exactly like these, that when on the wing they cannot be distinguished, although they frequent the same places and are often found intermingled. Other protected butterflies are of paler colours with dark stripes, and these are also closely imitated by other papilios. Altogether there are about fifteen species which thus closely resemble protected butterflies externally, although in structure and transformations they have no affinity with them. In some cases both sexes possess this resemblance, or “mimicry,” as it is termed, but most frequently it is the female only that is thus modified, especially when she lays her eggs on low-growing plants; while the male, whose flight is stronger and can take care of himself, does not possess it, and is often so different from his mate as to have been considered a distinct species. This leads us to the phenomenon of dimorphism and polymorphism, in which the females of one species present two or three different forms. Several such cases occur in the Malay Archipelago, in which there are two distinct kinds of females, sometimes even three, to a single male, which differs from either of them. In one case four females are known to one male, though only two of them appear to occur in one locality. These have been almost always described as distinct species, but observation has now proved them to be one, and it has further been noticed that each of the females, which are very unlike the male, resembles more or less closely some “protected" species. It has also been proved by experimental breeding that eggs laid by any one of these females are capable of producing butterflies of all the different forms, which in the few cases recorded are quite distinct from each other, without intermediate gradations. The local diversities of form are illustrated by outline figures (as regards two species of papilio from Celebes) in my “Malay Archipelago” (p. 216), and similar local peculiarities of colour, both in papilio and other groups, are described in my “Natural Selection and Tropical Nature” (pp. 384, 385), while extraordinary development of size in Amboyna is referred to at p. 307 of my “Malay Archipelago.” This brief outline of the paper will, perhaps, enable my readers to understand the intense interest I felt in working out all these strange phenomena, and showing how they could almost all be explained by that law of “Natural Selection” which Darwin had discovered many years before, and which I had also been so fortunate as to hit upon. The only other groups of insects upon which I did any systematic work were the families of Pieridae among butterflies and Cetoniidae among beetles. Of the former family, which contains our common whites, our brimstone and orange tip butterflies, I gave a list of all known from the Indian and Australian regions, describing fifty new species, mostly from my own collection. This paper is in the “Transactions of the Entomological Society for 1867,” and is illustrated by four coloured plates. The other paper, which is contained in the same volume, is a catalogue of the Cetoniidae (or Rosechafers, named after our common species) of the Malay Archipelago, in which I described seventy new species, the majority of which were collected by myself, and it is illustrated by four coloured plates, beautifully executed by the late Mr. E. W. Robinson, in which thirty-two of the species are figured. These two papers, filling about 200 pages of the society’s “Transactions,” occupied me for several months, and if I had not had wider and more varied interests— evolution, distribution, physical geography, anthropology, the glacial period, geological time, sociology, and several others—I might have spent the rest of my life upon similar work, for which my own collection afforded ample materials, and thus settled down into a regular “species-monger.” For even in this humble occupation there is a great fascination ; constant difficulties are encountered in unravelling the mistakes of previous describers who have had imperfect materials, while the detection of those minute differences, which often serve to distinguish allied species, and the many curious modifications of structure which characterize genera or their subdivisions, become intensely interesting, especially when, after weeks of study, a whole series of specimens, which seemed at first hardly distinguishable, are gradually separated into well-defined species, and order arises out of chaos. The series of papers on birds and insects now described, together with others on the physical geography of the archipelago and its various races of man, furnished me with the necessary materials for that general sketch of the natural history of the islands and of the various interesting problems which arise from its study, which has made my “Malay Archipelago” the most popular of my books. At the same time it opened up so many fields of research as to render me indisposed for further technical work in the mere description of my collections, which I should certainly never have been able to complete. I therefore now began to dispose of various portions of my insects to students of special groups, who undertook to publish lists of them with descriptions of the new species, reserving for myself only a few boxes of duplicates to serve as mementoes of the exquisite or fantastic organisms which I had procured during my eight years' wanderings. In order that my scientific friends might be able to see the chief treasures which I had brought home, I displayed a series of the rarest and most beautiful of my birds and butterflies in Mr. Sims's large photographic gallery in the same manner as I had found so effective with my New Guinea collections at Ternate. The entire series of my parrots, pigeons, and paradise birds, when laid out on long tables covered with white paper, formed a display of brilliant colours, strange forms, and exquisite texture that could hardly be surpassed; and when to these were added the most curious and beautiful among the warblers, flycatchers, drongos, starlings, gapers, ground thrushes, woodpeckers, barbets, cuckoos, trogons, kingfishers, hornbills, and pheasants, the general effect of the whole, and the impression it gave of the inexhaustible variety and beauty of nature in her richest treasure houses, was far superior to that of any collection of stuffed and mounted birds I have ever seen.

This mode of exhibiting bird skins is especially suitable for artificial light, and I believe that if a portion of the enormous wealth of the national collection in unmounted bird skins were used for evening display in the public galleries, it would be exceedingly attractive. Different regions or subregions might be illustrated by showing specimens of all the most distinct and remarkable species that characterize them, and each month during the winter a fresh series might be shown, and thus all parts of the world in turn represented. And in the case of insects the permanent series shown in the public galleries might be thus arranged, those of each region or of the well-marked subregions being kept quite separate. This would be not only more instructive, but very much more interesting, because such large numbers of persons have now visited or resided in various foreign countries, and a still larger number have friends or relatives living abroad, and all these would be especially interested in seeing the butterflies, beetles, and birds which are found there. In this way it would be possible to supply the great want in all public museums—a geographical rather than a purely systematic arrangement for the bulk of the collections exhibited to the public. The systematic portion so exhibited might be limited to the most distinctive types of organization, and these might be given in a moderate-sized room.

Having thus prepared the way by these preliminary studies, I devoted the larger portion of my time in the years 1867 and 1868 to writing my “Malay Archipelago.” I had previously read what works I could procure on the islands, and had made numerous extracts from the old voyagers on the parts I myself was acquainted with. These added much to the interest of my own accounts of the manners and character of the people, and by means of a tolerably full journal and the various papers I had written, I had no difficulty in going steadily on with my work. As my publishers wished the book to be well illustrated, I had to spend a good deal of time in deciding on the plates and

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