life, another becomes brown earlier, and in many species the last stage is
not wholly brown, a part remaining green. Whether this is a case of a
double adaptation, or whether the green is being gradually crowded out by
the brown, the fact remains that the same species, even the same
individual, can exhibit both variations. The case is the same with many of
the leaf-like Orthoptera, as, for instance, the praying mantis (Mantis
religiosa) which we have already mentioned.

But the best proofs are furnished by those often-cited cases in which the
insect bears a deceptive resemblance to another object. We now know many
such cases, such as the numerous imitations of green or withered leaves,
which are brought about in the most diverse ways, sometimes by mere
variations in the form of the insect and in its colour, sometimes by an
elaborate marking, like that which occurs in the Indian leaf-butterflies,
Kallima inachis. In the single butterfly-genus Anaea, in the woods of
South America, there are about a hundred species which are all gaily
coloured on the upper surface, and on the reverse side exhibit the most
delicate imitation of the colouring and pattern of a leaf, generally
without any indication of the leaf-ribs, but extremely deceptive
nevertheless. Anyone who has seen only one such butterfly may doubt
whether many of the insignificant details of the marking can really be of
advantage to the insect. Such details are for instance the apparent holes
and splits in the apparently dry or half-rotten leaf, which are usually due
to the fact that the scales are absent on a circular or oval patch so that
the colourless wing-membrane lies bare, and one can look through the spot
as through a window. Whether the bird which is seeking or pursuing the
butterflies takes these holes for dewdrops, or for the work of a devouring
insect, does not affect the question; the mirror-like spot undoubtedly
increases the general deceptiveness, for the same thing occurs in many
leaf-butterflies, though not in all, and in some cases it is replaced in