The Butterflies Of That Island Are In Many Cases
Characterised By A Peculiarity Of Outline, Which Distinguishes
Them At A Glance From Those Of Any Other Part Of The World.
It is
most strongly manifested in the Papilios and the Pieridae, and
consists in the forewings being either strongly curved or
abruptly bent near the base, or in the extremity being elongated
and often somewhat hooked.
Out of the 14 species of Papilio in
Celebes, 13 exhibit this peculiarity in a greater or less degree,
when compared with the most nearly allied species of the
surrounding islands. Ten species of Pieridae have the same
character, and in four or five of the Nymphalidae it is also very
distinctly marked. In almost every case, the species found in
Celebes are much larger than thane of the islands westward, and
at least equal to those of the Moluccas, or even larger. The
difference of form is, however, the most remarkable feature, as it
is altogether a new thing for a whole set of species in one
country to differ in exactly the same way from the 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.
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