168 TROPICAL NATURE, AND OTHER ESSAYS. 



to the curious changes in the colour of the chrysalis of 

 the small cabbage-butterfly (Pontia rapes) when the 

 caterpillars, just before their change, were confined in 

 boxes lined with different tints. Thus in black boxes 

 they were very dark, in white boxes nearly white ; and 

 he further showed that similar changes occurred in a 

 state of nature, chrysalises fixed against a white-washed 

 wall being nearly white ; against a red brick wall, reddish ; 

 against a pitched paling, nearly black. It has also been 

 observed that the cocoon of the emperor moth is either 

 white or brown, according to the colours surrounding it. 

 But the most extraordinary example of this kind of 

 change is that furnished by the chrysalis of an African 

 butterfly (Papilio Nireus), observed at the Cape by 

 Mrs. Barber, and described (with a coloured plate) in 

 the Transactions of the Entomological Society, 1874, 

 p. 519. 



This caterpillar feeds upon the orange tree, and 

 also upon a forest-tree ( Vepris lanceolata) which has a 

 lighter green leaf ; and its colour corresponds with that 

 of the leaves it feeds upon, being of a darker green 

 when it feeds on the orange. The chrysalis is usually 

 found suspended among the leafy twigs of its food-plant, 

 or of some neighbouring tree, but it is probably often 

 attached to larger branches ; and Mrs. Barber has dis- 

 covered that it has the property of acquiring the colour, 

 more or less accurately, of any natural object 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 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 (Banksia, 



