408
with different tints, just before their change into the
chrysalis condition. In black boxes they assumed a very
dark colour; in white boxes they became nearly white.
He also showed that a similar change took place in nature,
the chrysalis placed against a white wall being nearly
white, that against a red brick wall being reddish, and that
against a pitched paling being nearly black.
The caterpillar of an African butterfly feeds on the
orange tree and a forest tree which has a lighter green leaf,
and its colour corresponds with that of the leaves upon
which it feeds. Mrs. Barber has discovered that it has the
property of acquiring more or less accurately the colour of
any natural object that it may be in contact with. A
number of the caterpillars were placed in a case with a
glass cover, one side of the case being formed of the red
brick wall, the other side of yellowish wood. They were
fed on orange leaves, and a branch of the bottle-brush tree
was also placed in the case. When fully fed, some
attached themselves to the orange twigs, others to the
bottle-brush branch, and these all changed to green pupae
and each corresponded in tint to the leaves around it, the
one being a dark, the other a pale faded green. Another
attached itself to the wood, and the pupa became of the
same yellowish colour; while one fixed itself just where
the wood and the brick joined, and became one side red
the other side yellow.*
Change of organic colour may also be due to chemical
action.
“ Many of the complex substances which exist in animals and
plants are subject to changes of colour under the influence of light,
heat, and chemical change, and we know that chemical changes are
continually occurring during the physiological processes of develop
ment and growth.”—(Tropical Nature, p. 186.)
Wallace. Tropical Nature, pp. là’j-g.