The Action of Light upon the 
[■January, 
46 
Those which were kept in black boxes were nearly black, 
whilst such as had lived in white boxes were almost white. 
He observed corresponding changes in the same species in 
a state of Nature : chrysalids fixed against a whitewashed 
wall being whitish ; those secured to a red brick wall being 
reddish ; whilst those fixed against a pitched paling were 
nearly black. The cocoon of the emperor moth is also ob- 
served to be either white or brown, in accordance with the 
colours of surrounding objects. A still more decisive in- 
stance of such changes has been observed in the chrysalis 
of Papilio Nivens, a South-African butterfly which has been 
studied by Mrs. Barber. It acquires, more or less exactly, 
the colour of any contiguous objedt. “A number of the 
caterpillars were placed in a case with a glass cover, one 
side of the case being formed by a red brick wall, the other 
sides being of yellowish wood. They were fed on orange- 
leaves, and a branch of the bottle-brush tree (Banhsia) 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 ; but each 
corresponded exactly in tint to the leaves around it, the one 
being a dark and 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 brick joined, and became one side red, the other 
side yellow.” 
This Mr. Wallace pronounces “ a kind of natural photo- 
graphy, the particular coloured rays to which the fresh pupa 
is exposed in its soft semi-transparent condition effecting 
such a chemical change in the organic juices as to produce 
the same tint in the hardened skin.” This power of the 
pupa to assume the colour of closely adjacent objects, how- 
ever, is limited, since when Mrs. Barber surrounded one of 
her caterpillars with a piece of scarlet cloth the pupa dis- 
played its ordinary green tint, though the small red spots 
with which it is marked were rendered abnormally bright. 
It must be recorded, however, that these very interesting 
changes are confined to the chrysalis, and do not appear to 
have extended in any way to the mature butterfly. We 
have never been able to trace any modification in the colours 
of butterflies reared, for one generation, in abnormally” 
coloured light, nor, as far as we are aware, has any other 
observer been more successful. 
A correspondence has also been in some instances traced 
between the colours of animals and those of the localities 
which they inhabit and the food which they eat. Spiders 
