When We Consider The Wonderful Dissimilarity Of The Two Regions
In All Those Physical Conditions Which Were Once Supposed To
Determine the forms of life-Australia, with its open plains,
stony deserts, dried up rivers, and changeable temperate climate;
New
Guinea, with its luxuriant forests, uniformly hot, moist, and
evergreen - this great similarity in their productions is almost
astounding, and unmistakeably points to a common origin. 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. Such are the interesting sub-family of Longicorn coleoptera -
Tmesisternitae; one of the best-marked genera of Buprestidae -
Cyphogastra; and the beautiful weevils forming the genus
Eupholus. Among butterflies we have the genera Mynes, Hypocista,
and Elodina, and the curious eye-spotted Drusilla, of which last
a single species is found in Java, but in no other of the western
islands.
The facilities for the distribution of plants are still greater
than they are for insects, and it is the opinion of eminent
botanists, that no such clearly-defined regions pan be marked out
in botany as in zoology. The causes which tend to diffusion are
here most powerful, and have led to such intermingling of the
floras of adjacent regions that none but broad and general
divisions can now be detected. These remarks have an important
bearing on the problem of dividing the surface of the earth into
great regions, distinguished by the radical difference of their
natural productions. Such difference we now know to be the direct
result of long-continued separation by more or less impassable
barriers; and as wide oceans and great contrast: of temperature
are the most complete barriers to the dispersal of all
terrestrial forms of life, the primary divisions of the earth
should in the main serve for all terrestrial organisms. However
various may be the effects of climate, however unequal the means
of distribution; these will never altogether obliterate the
radical effects of long-continued isolation; and it is my firm
conviction, that when the botany and the entomology of New Guinea
and the surrounding islands become as well known as are their
mammals and birds, these departments of nature will also plainly
indicate the radical distinctions of the Indo-Malayan and Austro-
Malayan regions of the great Malay Archipelago.
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