VAEIABLE PEOTECTIVE EESEJVIBLANCE IN INSECTS 141 



Further experiments on the same subject 



During the summer of 1888 I conducted further 

 experiments upon the same subject. The results are 

 as yet imperfectly worked out, and are unpublished, 

 but I will shortly mention the chief conclusions. 

 Other glittering metallic surfaces, such as silver or tin, 

 do not produce anything like so striking an effect as 

 gold upon the pupae of the Small Tortoiseshell. It 

 seems probable that the yellow light reflected from 

 the gold is effective in preventing the formation of 

 pigment, and in thus producing the gilded chrysahdes, 

 just as the yellow light also prevents the appearance 

 of pigment and produces the bright green pupae among 

 the Pieridce. 



Two new species also were investigated, and proved 

 to be sensitive. The pupae of the Silver-washed 

 Fritillary {Argynnis paphia) can be rendered dark or 

 light in colour, although the metallic spots do not 

 seem to be affected. The pupae of the Large Tortoise- 

 shell (Vanessa polychloros) were also rendered dark 

 brown without metallic spots, or light reddish-brown 

 with the spots, by the use of appropriate surroundings. 

 The metallic spots could not be extended over the 

 pupal surface as in the case of the Small Tortoise- 

 Shnll. 



