For the purpose of insuring accuracy in comparisons with other islands, I shall confine myself to those groups which are best known, or which I have myself carefully studied. Beginning with the Papilionidae or Swallow-tailed butterflies, Celebes possesses 24 species, of which the large number of 18 are not found in any other island. If we compare this with Borneo, which out of 29 species has only two not found elsewhere, the difference is as striking as anything can be. In the family of the Pieridae, or white butterflies, the difference is not quite so great, owing perhaps to the more wandering habits of the group; but it is still very remarkable. Out of 30 species inhabiting Celebes, 19 are peculiar, while Java (from which more species are known than from Sumatra or Borneo), out of 37 species, has only 13 peculiar. The Danaidae are large, but weak-flying butterflies, which frequent forests and gardens, and are plainly but often very richly coloured. Of these my own collection contains 16 species from Celebes and 15 from Borneo; but whereas no less than 14 are confined to the former island, only two are peculiar to the latter. The Nymphalidae are a very extensive group, of generally strong-winged and very bright-coloured butterflies, very abundant in the tropics, and represented in our own country by our Fritillaries, our Vanessas, and our Purple-emperor. Some months ago I drew up a list of the Eastern species of this group, including all the new ones discovered by myself, and arrived at the following comparative results:—
Species of Species peculiar to Percentage
Nymphalidae. each island. of peculiar Species.
Java..... 70...... 23.......... 33
Borneo.... 52...... 15.......... 29
Celebes ... 48...... 35.......... 73
The Coleoptera are so extensive that few of the groups have yet been carefully worked out. I will therefore refer to one only, which I have myself recently studied—the Cetoniadae or Rose-chafers—a group of beetles which, owing to their extreme beauty, have been much sought after. From Java 37 species of these insects are known, and from Celebes only 30; yet only 13, or 35 percent, are peculiar to the former island, and 19, or 63 percent, to the latter.
The result of these comparisons is, that although Celebes is a single, large island with only a few smaller ones closely grouped around it, we must really consider it as forming one of the great divisions of the Archipelago, equal in rank and importance to the whole of the Moluccan or Philippine groups, to the Papuan islands, or to the Indo-Malay islands (Java, Sumatra, Borneo, and the Malay peninsula). Taking those families of insects and birds which are best known, the following table shows the comparison of Celebes with the other groups of islands:—
PAPILIONIDAE AND HAWKS, PARROTS, AND
PERIDAE PIGEONS.
Percent of peculiar Percent of peculiar
Species. Species.
Indo-Malay region.... 56.......... 54
Philippine group .... 66.......... 73
Celebes......... 69.......... 60
Moluccan group ..... 52.......... 62
Timor group....... 42.......... 47
Papuan group ...... 64.......... 74
These large and well-known families well represent the general character of the zoology of Celebes; and they show that this island is really one of the most isolated portions of the Archipelago, although situated in its very centre.
But the insects of Celebes present us with other phenomena more curious and more difficult to explain than their striking individuality. The butterflies of that island are in many cases characterised by a peculiarity of outline, which distinguishes them at a glance from those of any other part of the world. It is most strongly manifested in the Papilios and the Pieridae, and consists in the forewings being either strongly curved or abruptly bent near the base, or in the extremity being elongated and often somewhat hooked. Out of the 14 species of Papilio in Celebes, 13 exhibit this peculiarity in a greater or less degree, when compared with the most nearly allied species of the surrounding islands. Ten species of Pieridae have the same character, and in four or five of the Nymphalidae it is also very distinctly marked. In almost every case, the species found in Celebes are much larger than those of the islands westward, and at least equal to those of the Moluccas, or even larger. The difference of form is, however, the most remarkable feature, as it is altogether a new thing for a whole set of species in one country to differ in exactly the same way from the corresponding sets in all the surrounding countries; and it is so well marked, that without looking at the details of colouring, most Celebes Papilios and many Pieridae, can be at once distinguished from those of other islands by their form alone.
The outside figure of each pair here given, shows the exact size and form of the fore-wing in a butterfly of Celebes, while the inner one represents the most closely allied species from one of the adjacent islands. Figure 1 shows the strongly curved margin of the Celebes species, Papilio gigon, compared with the much straighter margin of Papilio demolion from Singapore and Java. Figure 2 shows the abrupt bend over the base of the wing in Papilio miletus of Celebes, compared with the slight curvature in the common Papilio sarpedon, which has almost exactly the same form from India to New Guinea and Australia. Figure 3 shows the elongated wing of Tachyris zarinda, a native of Celebes, compared with the much shorter wing of Tachyris nero, a very closely allied species found in all the western islands. The difference of form is in each case sufficiently obvious, but when the insects themselves are compared, it is much more striking than in these partial outlines.
From the analogy of birds, we should suppose that the pointed wing gave increased rapidity of flight, since it is a character of terns, swallows, falcons, and of the swift-flying pigeons. A short and rounded wing, on the other hand, always accompanies a more feeble or more laborious flight, and one much less under command. We might suppose, therefore, that the butterflies which possess this peculiar form were better able to escape pursuit. But there seems no unusual abundance of insectivorous birds to render this necessary; and as we cannot believe that such a curious peculiarity is without meaning, it seems probable that it is the result of a former condition of things, when the island possessed a much richer fauna, the relics of which we see in the isolated birds and Mammalia now inhabiting it; and when the abundance of insectivorous creatures rendered some unusual means of escape a necessity for the large-winged and showy butterflies. It is some confirmation of this view, that neither the very small nor the very obscurely coloured groups of butterflies have elongated wings, nor is any modification perceptible in those strong-winged groups which already possess great strength and rapidity of flight. These were already sufficiently protected from their enemies, and did not require increased power of escaping from them. It is not at all clear what effect the peculiar curvature of the wings has in modifying flight.
Another curious feature in the zoology of Celebes is also worthy of attention. I allude to the absence of several groups which are found on both sides of it, in the Indo-Malay islands as well as in the Moluccas; and which thus seem to be unable, from some unknown cause, to obtain a footing in the intervening island. In Birds we have the two families of Podargidae and Laniadae, which range over the whole Archipelago and into Australia, and which yet have no representative in Celebes. The genera Ceyx among Kingfishers, Criniger among Thrushes, Rhipidura among Flycatchers, Calornis among Starlings, and Erythrura among Finches, are all found in the Moluccas as well as in Borneo and Java—but not a single species belonging to any one of them is found in Celebes. Among insects, the large genus of Rose-chafers, Lomaptera, is found in every country and island between India and New Guinea, except Celebes. This unexpected absence of many groups, from one limited district in the very centre of their area of distribution, is a phenomenon not altogether unique, but, I believe, nowhere so well marked as in this case; and it certainly adds considerably to the strange character of this remarkable island.