Adjustment of colour in various ptipse, etc. 389 



Local differences ia susceptibility are of course possible, 

 and an enquiry directed along this line might lead to 

 results of high interest. 



It is a great pleasure to me to see this species, upon 

 which so much doubt has been thrown — in the first place 

 in the discussion which followed Mr. T. W. Wood's 

 communication to this Society in 1867 (Proc. pp. xcix — 

 ci), and nineteen years later as the results of my experi- 

 ments — now finally proved beyond doubt to be susceptible 

 to the colours of its environment. This result, which we 

 owe to Mr. Merrifield, is a further warning against the 

 errors into which we are liable to be led by relying, as Mr. 

 Bond did (in the 1867 discussion), upon a general im- 

 pression gathered from a wide experience not specially 

 directed towards the solution of the problem, as I did, 

 upon an insufficient number of individuals subjected to 

 experiment. 



C— EXPERIMENTS UPON THE PUP^ OF 

 Papilio jpodalirms. (CoRA B. Sanders and E. B. P.) 



Five full-fed larvae of this species were found by us 

 in Switzerland, between Visp and Stalden, on July 22nd, 

 1898. They were all, except one, of the usual yellow- 

 striped green form. The single exception was brownish- 

 green with many red spots somewhat similar to those 

 which occur upon certain forms of the larvae of Smerinthus 

 ocellatns and <S^. populi. It is possible that the darkened 

 ground colour was due to changes preparatory to pupa- 

 tion, or perhaps to ill-health, as the larva died without 

 pupating. Two of the larvse were placed in a white 

 muslin bas^ and offered srreen reeds together with the 

 green twigs and leaves of the food-plant : three were 

 placed in a black net bag, and provided with dark brown 

 branches, as well as the food-plant. In a few days four 

 of them pupated, one being fixed to the white muslin 

 and three to the black net. 



It was immediately seen that the latter were far darker 

 than the former. A careful comparison was made on 

 May 3rd, 1899. 



The pupa which had been fixed to white muslin was a 

 pale dull orange tint, especially dull over the wings. Of 

 the other three which had been fixed to black net, one 

 was also dull orange but of a distinctly darker shade, 



