Travel Reference
In-Depth Information
The end of the upper wings terminates in a fine point, just as the leaves of many tropical
shrubs and trees are pointed, while the lower wings are somewhat more obtuse, and are
lengthened out into a short thick tail. Between these two points there runs a dark curved line
exactly representing the midrib of a leaf, and from this radiate on each side a few oblique
marks which well imitate the lateral veins. These marks are more clearly seen on the outer
portion of the base of the wings, and on the inner side towards the middle and apex, and
they are produced by striæ and markings which are very common in allied species, but
which are here modified and strengthened so as to imitate more exactly the venation of a
leaf. The tint of the under surface 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 sup-
ported by the middle pair of legs, which are not noticed among the twigs and fibres that sur-
round it. The head and antennæ are drawn back between the wings so as to be quite con-
cealed, 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 every one 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 un-
doubtedly 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 examin-
ing 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 be-
lieve that fungi have grown 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
