140 THE COLOURS OF ANIMALS 



Variable Protective Resemblance in the pupae of the 

 Pieridse. 



The susceptibility of the two species of Garden 

 White Butterflies (Pieris brassicce and P. rapce) was 

 also investigated in the same season (1886), and the 

 results of previous observers were confirmed and 

 extended. Many colours were employed, and it was 

 found that the light reflected from yellow and orange 

 surroundings was very potent in producing bright 

 green varieties of the chrysalides of both species. It 

 is therefore probable that when the light reflected 

 from green leaves produces this effect in nature, the 

 yellow and orange constituents of the light form 

 the stimuli. When, therefore, these constituents are 

 made use of nearly alone, they produce still more 

 marked effects. Black and white backgrounds caused 

 the pupae of both species to become dark and light 

 respectively, and all other colours except yellow and 

 orange produced more or less dark pupae. 



Experiments were made upon P. rapce to ascertain 

 the susceptible period, the larvae being transferred as 

 in the case of the Small Tortoiseshell. The results 

 were as in the latter : the larva is sensitive and not 

 the pupa, and the time of chief susceptibility is during 

 stage ii. 



A few larvae of P. rapce were blinded, but the chry- 

 salides were similar to those produced by normal larvae. 



