The Malay archipelago : the land of the orang-utan ... - Wallace Online

XVIII.] NATURAL HISTORY OF CELEBES. 213Here again we have a resemblance to the Wart-hog.s of x\frica,whose upper canines grow outwards and curve up so as to forma transition from the usual mode of growth to that of theBabirusa. In otlier respects there seems no affinity betweenthese animals, and the Babirusa stands completely isolated,having no resemblance to the pigs of any other part of theworld. It is found all over Celebes and in the Sula islands, andalso in Bouru, the only spot beyond the Celebes group to whichit extends ;and which island also shows some affinity to theSula islands in its birds, indicating perhaps a closer connexionbetween them at some former i^eriod than now exists.The other terrestrial mammals of Celebes are, five species ofsquirrels, which are all distinct from those of Java and Borneo,and mark the furthest eastward range of the genus in the tropics ;and two of Eastern opossums (Cuscus), which are different fromthose of the Moluccas, and mark the furthest westward extensionof this genus and of the Marsupial order. Thus we seethat the Mammalia of Celebes are no less individual and remarkablethan the birds, since three of the largest and most interestingspecies have no near allies in surrounding countries, butseem vaguely to indicate a relation to the African continent.Many groups of insects appear to be especially subject tolocal influences, their forms and colours changing with eachchange of conditions, or even with a change of locality wherethe conditions seem almost identical. We should thereforeanticipate that the individuality manifested in the higheranimals would be still more prominent in these creatures withless stable organisms. On the other hand, however, we have toconsider that the dispersion and migration of insects is muchmore easilj^ effected than that of mammals or even of birds.They are much more likely to be carried away by violent winds ;their eggs may be carried on leaves either by storms of wind orby floating trees, and their larvje and pupte often buried intrunks of trees or enclosed in waterproof cocoons, may be floatedfor days or weeks uninjured over the ocean. Tliese facilities ofdistribution tend to assimilate the productions of adjacent landsin two ways : first, by direct mutual interchange of species ;and secondly, by repeated immigrations of fresh Individuals ofa species common to other islands, which by intercrossing tendto obliterate the changes of form and colour, which differencesof conditions might otherwise produce. Bearing these factsin mind, we shall find that the individuality of the insectsof Celebes is even greater than we have any reason to expect.For the purpose of insuring accuracy in comparisons withother islands, I shall confine myself to those groups which arebest known, or which I have myself carefully studied. Beginningwith the Papilionidaj or Swallow-tailed butterflies, Celebespossesses 24 species, of which the large number of 18 are notfound in any other island. If we compare this with Borneo,which out of 29 species has only two not found elsewhere, the