Adjustment of colour in various pu^-iie, etc. 405 



surfaces many distinct shades ranging through Hack, 

 brown, and grey ; and also on the provision of the appro- 

 priate stimuli can become white or green (Trans. Ent. Soc. 

 1892, I. c). 



The reactions of the pupse of Pieris napi to the colours 

 employed agree well with the observations recorded in the 

 case of other susceptible pupse if allowance be made for the 

 wider range of controllable modification. 



^.—EXPERIMENTS UPON THE PUP^E OF 



Pieris hrctssica?-. 



1. Experiments upon the Winter Pup^e of 

 Pieris hrassicfe. (F. M.) 



I took advantage of the pestilential abundance of the 

 larvae of this species to experiment on them and I exhibit 

 samples of the re.sults, which will be described so far as 

 necessary in the following section. It is the less necessary 

 to refer to them at any length, because the species has 

 been so fully experimented on by Prof. Poulton as de- 

 scribed in the papers before referred to, and as will appear 

 later in this memoir, also during the present year (1898). 

 But I would call attention to one feature, that has been 

 carried perhaps a little further than had been done before, 

 in my experiments on this species and the next referred 

 to, P. rapm. It seemed a fair inference both from Prof. 

 Poul ton's paper and from my personal observation of the ex- 

 periments with darkness on the other two species, that the 

 positive aiDplication by reflection or otherwise of some 

 decided colour (including black and white among colours) 

 was necessary to affect the colour of the pupse in a marked 

 degree. Accordingly I tried the experiment of surrounding 

 some pupse with clear glass away from all near reflecting 

 objects. For this purpose I placed the full-fed larvae in clear 

 glass cylinders covered by clear glass and resting on a clear 

 glass sheet several inches above the table, so that light 

 reached them all round. They were placed on a table 

 near the window. It will be observed that in the case 

 both of this species and the next, the pupse of the larvae 

 thus exposed to uncoloured light on all sides, rather closely 

 resemble those in darkness, the former being somewhat 

 darker than the later. In the case of P. napi darkness pro- 

 duced much variety of colour : of seven all but one are green 

 but of somewhat varying tint, and the one bone-coloured 

 and two of the green ones are much spotted with dark- 



