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.