PEOTECXIVB COLOBATION. 137 



surface upon which they rest. Apparently Mr. T. W. Wood 

 was the first to call the attention of naturalists to this fact. 

 He exhibited a series of chrysalids of the Swallow-tailed 

 Butterfly and of the Garden Whites, which were darker or 

 lighter in colour in correspondence with the situations where 

 they were found. The subject has been recently studied in 

 great detail by Mr. Poulton, who has iiublished an important 

 and beautifully illustrated memoir,* describing his exjjeriments. 

 These experiments dealt with several species ; among others 

 with the common Tortoiseshell Butterfly. 



When the caterpillars were compelled to " spin up " upon a 

 •dark ground they were extremely dark in colour, with, at 

 most, only a trace of gold spots. With white surroundings 

 the pupEe were light-coloured,t and the' gold spots were often so 

 ■greatly developed that "the whole surface of the pupa glittered 

 with an apparent metallic lustre." 



A point to be noticed is that colours were produced which 

 are " very rarely [the italics Mr. Poulton's] seen in nature." 

 Prof. Eimer speaks % of the production of red-coloured chry- 

 ■ salids, when the larva was enveloped by a red cloth at the 

 time of change ; but he does not mention the species of butter- 

 fly in which these effects were artificially produced. Clearly, 

 therefore, the pupa is highly susceptible to the colours of sur- 

 rounding objects, and to an extent which is not limited by the 

 colours of its usual surroundings. Mr. Morris succeeded § in 

 producing white, red, salmon, black, and blue pupse of Danais 

 •chrysippus ; they are only green or pink in nature. 



The metallic colour of the pupa, which is so often met witli 



* " Philosophical Transactions," 1889. 



t By an ingenious arrangement the pupa was also made to assume a 

 light colour upon one half and a dark colour upon the other. 

 \ Loc. cif., p. 144. 

 § Journ. Bombay Nat. Hist. Snc, 1890. 



