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 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 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.
In Sumatra, monkeys are very abundant, and at Lobo Kaman they used to
frequent the trees which overhang the guard-house, and give me a fine
opportunity of observing their gambols. Two species of Semnopithecus
were most plentiful--monkeys of a slender form, with very long
tails. Not being much shot at they are rather bold, and remain quite
unconcerned when natives alone are present; but when I came out to look
at them, they would stare for a minute or two and then make off. They
take tremendous leaps from the branches of one tree to those of another
a little lower, and it is very amusing when one strong leader takes a
bold jump, to see the others following with more or less trepidation;
and it often happens that one or two of the last seem quite unable to
make up their minds to leap until the rest are disappearing, when, as
if in desperation at being left alone, they throw themselves frantically
into the air, and often go crashing through the slender branches and
fall to the ground.
A very curious ape, the Siamang, was also rather abundant, but it is
much less bold than the monkeys, keeping to the virgin forests and
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