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 avoiding villages. This
species is allied to the little long-armed apes of the genus Hylobates, but is
considerably larger, and differs from them by having the two first fingers of the
feet united together, nearly to the end as does its Latin name, Siamanga
syndactyla. It moves much more slowly than the active Hylobates, keeping
lower down in trees, and not indulging in such tremendous leaps; but it is still
very active, and by means of its immense long arms, five feet six inches across
in an adult about three feet high, can swing itself along among the trees at a great
rate. I purchased a small one, which had been caught by the natives and tied up