A very curious fact, not hitherto sufficiently noticed, is the appearance of a pure Malay element in the birds of New Guinea. We find two species of Eupetes, a curious Malayan genus allied to the forked-tail water-chats; two of Alcippe, an Indian and Malay wren-like form; an Arachnothera, quite resembling the spider-catching honeysuckers of Malacca; two species of Gracula, the Mynahs of India; and a curious little black Prionochilus, a saw-billed fruit pecker, undoubtedly allied to the Malayan form, although perhaps a distinct genus. Now not one of these birds, or anything allied to them, occurs in the Moluccas, or (with one exception) in Celebes or Australia; and as they are most of them birds of short flight, it is very difficult to conceive how or when they could have crossed the space of more than a thousand miles, which now separates them from their nearest allies. Such facts point to changes of land and sea on a large scale, and at a rate which, measured by the time required for a change of species, must be termed rapid. By speculating on such changes, we may easily see how partial waves of immigration may have entered New Guinea, and how all trace of their passage may have been obliterated by the subsequent disappearance of the intervening land.
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.
