There is nothing that the study of geology teaches us that is more certain or more impressive than the extreme instability of the earth's surface. Everywhere beneath our feet we find proofs that what is land has been sea, and that where oceans now spread out has once been land; and that this change from sea to land, and from land to sea, has taken place, not once or twice only, but again and again, during countless ages of past time. Now the study of the distribution of animal life upon the present surface of the earth, causes us to look upon this constant interchange of land and sea—this making and unmaking of continents, this elevation and disappearance of islands—as a potent reality, which has always and everywhere been in progress, and has been the main agent in determining the manner in which living things are now grouped and scattered over the earth's surface. And when we continually come upon such little anomalies of distribution as that just now described, we find the only rational explanation of them, in those repeated elevations and depressions which have left their record in mysterious, but still intelligible characters on the face of organic nature.
The insects of New Guinea are less known than the birds, but they seem almost equally remarkable for fine forms and brilliant colours. The magnificent green and yellow Ornithopterae are abundant, and have most probably spread westward from this point as far as India. Among the smaller butterflies are several peculiar genera of Nymphalidae and Lycaenidae, remarkable for their large size, singular markings, or brilliant coloration. The largest and most beautiful of the clear-winged moths (Cocytia d'urvillei) is found here, as well as the large and handsome green moth (Nyctalemon orontes). The beetles furnish us with many species of large size, and of the most brilliant metallic lustre, among which the Tmesisternus mirabilis, a longicorn beetle of a golden green colour; the excessively brilliant rose-chafers, Lomaptera wallacei and Anacamptorhina fulgida; one of the handsomest of the Buprestidae, Calodema wallacei; and several fine blue weevils of the genus Eupholus, are perhaps the most conspicuous. Almost all the other orders furnish us with large or extraordinary forms. The curious horned flies have already been mentioned; and among the Orthoptera the great shielded grasshoppers are the most remarkable. The species here figured (Megalodon ensifer) has the thorax covered by a large triangular horny shield, two and a half inches long, with serrated edges, a somewhat wavy, hollow surface, and a faun median line, so as very closely to resemble a leaf. The glossy wing-coverts (when fully expanded, more than nine inches across) are of a fine green colour and so beautifully veined as to imitate closely some of the large shining tropical leaves. The body is short, and terminated in the female by a long curved sword-like ovipositor (not seen in the cut), and the legs are all long and strongly-spined. These insects are sluggish in their motions, depending for safety on their resemblance to foliage, their horny shield and wing-coverts, and their spiny legs.
The large islands to the east of New Guinea are very little known, but the occurrence of crimson lories, which are quite absent from Australia, and of cockatoos allied to those of New Guinea and the Moluccas, shows that they belong to the Papuan group; and we are thus able to define the Malay Archipelago as extending eastward to the Solomon's Islands. New Caledonia and the New Hebrides, on the other hand, seem more nearly allied to Australia; and the rest of the islands of the Pacific, though very poor in all forms of life, possess a few peculiarities which compel us to class them as a separate group. Although as a matter of convenience I have always separated the Moluccas as a distinct zoological group from New Guinea, I have at the same time pointed out that its fauna was chiefly derived from that island, just as that of Timor was chiefly derived from Australia. If we were dividing the Australian region for zoological purposes alone, we should form three great groups: one comprising Australia, Timor, and Tasmania; another New Guinea, with the islands from Bouru to the Solomon's group; and the third comprising the greater part of the Pacific Islands.
The relation of the New Guinea fauna to that of Australia is very close. It is best marked in the Mammalia by the abundance of marsupials, and the almost complete absence of all other terrestrial forms. In birds it is less striking, although still very clear, for all the remarkable old-world forms which are absent from the one are equally so from the other, such as Pheasants, Grouse, Vultures, and Woodpeckers; while Cockatoos, Broad-tailed Parrots, Podargi, and the great families of the Honeysuckers and Brush-turkeys, with many others, comprising no less than twenty-four genera of land-birds, are common to both countries, and are entirely confined to them.
When we consider the wonderful dissimilarity of the two regions in all those physical conditions which were once supposed to determine the forms of life-Australia, with its open plains, stony deserts, dried up rivers, and changeable temperate climate; New Guinea, with its luxuriant forests, uniformly hot, moist, and evergreen—this great similarity in their productions is almost astounding, and unmistakeably points to a common origin. The resemblance is not nearly so strongly marked in insects, the reason obviously being, that this class of animals are much more immediately dependent on vegetation and climate than are the more highly organized birds and Mammalia. Insects also have far more effective means of distribution, and have spread widely into every district favourable to their development and increase. The giant Ornithopterae have thus spread from New Guinea over the whole Archipelago, and as far as the base of the Himalayas; while the elegant long-horned Anthribidae have spread in the opposite direction from Malacca to New Guinea, but owing to unfavourable conditions have not been able to establish themselves in Australia. That country, on the other hand, has developed a variety of flower-haunting Chafers and Buprestidae, and numbers of large and curious terrestrial Weevils, scarcely any of which are adapted to the damp gloomy forests of New Guinea, where entirely different forms are to be found. There are, however, some groups of insects, constituting what appear to be the remains of the ancient population of the equatorial parts of the Australian region, which are still almost entirely confined to it. Such are the interesting sub-family of Longicorn coleoptera—Tmesisternitae; one of the best-marked genera of Buprestidae—Cyphogastra; and the beautiful weevils forming the genus Eupholus. Among butterflies we have the genera Mynes, Hypocista, and Elodina, and the curious eye-spotted Drusilla, of which last a single species is found in Java, but in no other of the western islands.
The facilities for the distribution of plants are still greater than they are for insects, and it is the opinion of eminent botanists, that no such clearly-defined regions pan be marked out in botany as in zoology. The causes which tend to diffusion are here most powerful, and have led to such intermingling of the floras of adjacent regions that none but broad and general divisions can now be detected. These remarks have an important bearing on the problem of dividing the surface of the earth into great regions, distinguished by the radical difference of their natural productions. Such difference we now know to be the direct result of long-continued separation by more or less impassable barriers; and as wide oceans and great contrast: of temperature are the most complete barriers to the dispersal of all terrestrial forms of life, the primary divisions of the earth should in the main serve for all terrestrial organisms. However various may be the effects of climate, however unequal the means of distribution; these will never altogether obliterate the radical effects of long-continued isolation; and it is my firm conviction, that when the botany and the entomology of New Guinea and the surrounding islands become as well known as are their mammals and birds, these departments of nature will also plainly indicate the radical distinctions of the Indo-Malayan and Austro-Malayan regions of the great Malay Archipelago.
CHAPTER XL. THE RACES OF MAN IN THE MALAY ARCHIPELAGO.
PROPOSE to conclude this account of my Eastern travels, with a short statement of my views as to the races of man which inhabit the various parts of the Archipelago, their chief physical and mental characteristics, their affinities with each other and with surrounding tribes, their migrations, and their probable origin.
Two very strongly contrasted races inhabit the Archipelago—the Malays, occupying almost exclusively the larger western half of it, and the Papuans, whose headquarters are New Guinea and several of the adjacent islands. Between these in locality, are found tribes who are also intermediate in their chief characteristics, and it is sometimes a nice point to determine whether they belong to one or the other race, or have been formed by a mixture of the two.