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