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346 TROPICAL NATUREThis caterpillarfeeds upon the orange tree, and also upona forest tree (Vepris lanceolata) which has a lighter greenleaf ;and its colour corresponds with that of the leaves itfeeds upon, being of a darker green when it feeds on theorange. The chrysalis is usually found suspended among theleafy twigs of its food-plant, or of some neighbouring tree,but it is probably often attached to larger branches ;and Mrs.Barber has discovered that it has the property of acquiringthe colour, more or less accurately, of any natural object itmay be in contact with. A number of the caterpillars wereplaced in a case with a glass cover, one side of the case beingformed by a red brick wall, the other sides being of yellowishwood. They were fed on orange leaves, and a branch of thebottle -brush tree (Banksia sp.) was also placed in the case.When fully fed, some attached themselves to the orangetwigs, others to the bottle-brush branch, and these all changedto green pupae, but each corresponded exactly in tint to theleaves around it, the one being dark, the other a pale fadedgreen. Another attached itself to the wood^ and the pupabecame of the same yellowish colour, while one fixed itselfjust where the wood and brick joined, and became one sidered, the other side yellow These remarkable changes would!perhaps not have been credited had it not been for the previousobservations of Mr. Wood ;but the two support eachother, and oblige us to accept them as actual phenomena. Itis a kind of natural photography, the particular coloured raysto which the fresh pupa is exposed in its soft, semi-transparentcondition effecting such a chemical change in the organicjuices as to produce the same tint in the hardened skin. Itis interesting, however, to note that the range of colour thatcan be acquired seems to be limited to those of naturalobjects to which the pupa is likely to be attached, for whenMrs. Barber surrounded one of the caterpillars with a pieceof scarlet cloth no change of colour at all was produced, thepupa being of the usual green tint, but the small red spotswith which it is marked were brighter than usual. 11 Mr. E. B. Poulton has since greatly extended these observations, both inpupae and larvae, with very remarkable results. See Proc. of the RoyalSociety, No. 243, 1886 Transactions ; of the Royal Society, vol. clxxviii. B.,pp. 311-441. These are briefly described in Darwinism, p. 197, and morefully in a volume by Mr. Poulton on The Colours of Animals, 1890.