On the other hand, however, we have to consider that the dispersion and migration of insects is much more easily 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 or by floating trees, and their larvae and pupae, often buried in trunks of trees or enclosed in waterproof cocoons, may be floated for days or weeks uninjured over the ocean.

These facilities of distribution tend to assimilate the productions of adjacent lands in two ways: first, by direct mutual interchange of species; and secondly, by repeated immigrations of fresh individuals of a species common to other islands, which by intercrossing, tend to obliterate the changes of form and colour, which differences of conditions might otherwise produce.

Bearing these facts in mind, we shall find that the individuality of the insects of Celebes is even greater than we have any reason to expect.
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.