COLOURS OF ANIMALS. 169 



sp.) 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 

 pupse ; but each corresponded exactly in tint to the leaves 

 around it, the one being 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 brick joined, and became 

 one side red, the other side yellow ! These remark- 

 able changes would perhaps not have been credited had 

 it not been for the previous observations of Mr. Wood ; 

 but the two support each other, and oblige us to accept 

 them as actual phenomena. It is a kind of natural 

 photography, the particular coloured rays to which the 

 fresh pupa is exposed in its soft, semi-transparent con- 

 dition, effecting such a chemical change in the organic 

 juices as to produce the same tint in the hardened skin. 

 It is interesting however to note, that the range of 

 colour that can be acquired seems to be limited to those 

 of natural objects to which the pupa is likely to be 

 attached ; for when Mrs. Barber surrounded one of the 

 caterpillars with a piece of scarlet cloth no change of 

 colour at all was produced, the pupa being of the usual 

 green tint, but the small red spots with which it is 

 marked were brighter than usual. 



Many other cases are known among insects in which 

 the same species acquires a different tint according 

 to its surroundings ; this being particularly marked in 

 some South African locusts, which correspond with the 

 colour of the soil wherever they are found. There are 

 also many caterpillars which feed on two or more plants, 

 and which vary in colour accordingly. A number of such 



