The Tint Of The Undersurface Varies Much,
But It Is Always Some Ashy Brown Or Reddish Colour, Which Matches
With Those Of Dead Leaves.
The habit of the species is always to
rest on a twig and among dead or dry leaves, and
In this position
with the wings closely pressed together, their outline is exactly
that of a moderately-sized leaf, slightly curved or shrivelled.
The tail of the hind wings forms a perfect stalk, and touches the
stick while the insect is supported by the middle pair of legs,
which are not noticed among the twigs and fibres that surround
it. The head and antennae are drawn back between the wings so as
to be quite concealed, and there is a little notch hollowed out
at the very base of the wings, which allows the head to be
retracted sufficiently. All these varied details combine to
produce a disguise that is so complete and marvellous as to
astonish everyone who observes it; and the habits of the insects
are such as to utilize all these peculiarities, and render them
available in such a manner as to remove all doubt of the purpose
of this singular case of mimicry, which is undoubtedly a
protection to the insect.
Its strong and swift flight is sufficient to save it from its enemies
when on the wing, but if it were equally conspicuous when at rest it
could not long escape extinction, owing to the attacks of the
insectivorous birds and reptiles that abound in the tropical forests.
A very closely allied species, Kallima inachis, inhabits India, where
it is very common, and specimens are sent in every collection from
the Himalayas. On examining a number of these, it will be seen that
no two are alike, but all the variations correspond to those of
dead leaves. Every tint of yellow, ash, brown, and red is found
here, and in many specimens there occur patches and spots formed
of small black dots, so closely resembling the way in which
minute fungi grow on leaves that it is almost impossible at first
not to believe that fungi have gown on the butterflies
themselves!
If such an extraordinary adaptation as this stood alone, it would
be very difficult to offer any explanation of it; but although it
is perhaps the most perfect case of protective imitation known,
there are hundreds of similar resemblances in nature, and from
these it is possible to deduce a general theory of the manner in
which they have been slowly brought about. The principle of
variation and that of "natural selection," or survival of the
fittest, as elaborated by Mr. Darwin in his celebrated "Origin of
Species," offers the foundation for such a theory; and I have
myself endeavoured to apply it to all the chief cases of
imitation in an article published in the "Westminster Review" for
1867, entitled, "Mimicry, and other Protective Resemblances
Among Animals," to which any reader is referred who wishes to
know more about this subject.
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