In cases where the outward
resemblance of some feeble animal to a widely different and
well-protected species, or to some object like a leaf or stick, and
where such resemblance is manifestly advantageous and has reacted on and
modified the life habits, it is conceivable that slight spontaneous
variations in the structure and colouring of the unprotected species
have been taken advantage of by the principle of natural selection, and
a case of "mimicry" set up, to become more and more perfect in time, as
successive casual variations in the same direction increased the
resemblance.
The stick-insect is perhaps the most perfect example where resemblance
to an inanimate object has been the result aimed at, so to speak, by
nature; the resemblance of the volucella fly to the humble-bee, on which
it is parasitical, is the most familiar example of one species growing
like another to its own advantage, since only by means of its deceptive
likeness to the humble-bee is it able to penetrate into the nest with
impunity. These two cases, with others of a similar character, were
first called cases of "mimicry" by Kirby and Spence, in their
ever-delightful _Introduction to Entomology--_an old book, but,
curiously enough in these days of popular treatises on all matters of
the kind, still the only general work on insects in the English language
which one who is not an entomologist can read with pleasure.
A second case of mimicry not yet noticed by any naturalist is seen in
another grasshopper, also common in La Plata (Rhomalea speciosa of
Thun-berg).
Pages:
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137