Adjustment of colour in various 2Jup^> ^^^- ^79 



secured by three ties of thread and on the tops by a sheet 

 of clear glass. In the case however of the dark sticks the 

 bottom was of dark cork carpet, and these cylinders were 

 clear all round, with a sheet of clear glass on the top. 



In order not to crowd the larvae, it was my practice to 

 transfer them, when spun up on the sticks, to wide-mouthed 

 Bordeaux plum-bottles of clear glass having a greenish hue, 

 of about the same size as the cylinders, but fitted for two- 

 thirds of their circumference with coloured paper inside 

 instead of outside, and I sometimes transferred larvse direct 

 from the compartments of the breeding-cage to these bottles, 

 as pupating against glass in front of coloured paper did 

 not appear to me to be the same thing in effect as pupat- 

 ing against the coloured paper. In tliese bottles the 

 coloured paper was inside, and therefore nearer the larvae 

 than in the cylinders. The sticks in the bottles could not 

 be prevented from shifting as heavy larvae crawled over 

 them, and the larvae appeared to dislike this, and to be 

 more restless and slower in pupating than when the sticks 

 were fixed. 



The cylinders and bottles were placed within a few 

 inches of the window above referred to, or of another 

 window having the same aspect, but only about 4 feet 

 high by 3 feet wide. As the objects in both were neces- 

 sarily near the light, and, except in those given over to 

 black, light, coloured or uncoloured, was admitted all round 

 and by the tops, the larvae in these were as a rule exposed 

 to much more light, both direct and reflected, than those 

 in the breeding-cages. 



I also lined a clear glass saucer with green carrot-tops 

 and placed it in a second saucer with green carrot-tops, 

 among which some larvae pupated, the surface being covered 

 with a sheet of clear glass. 



Most of the machaon larvae in the cylinders or bottles 

 spun up against the coloured sticks provided for them, but 

 in a few cases they spun either against the glass where it 

 was covered outside by coloured paper or against the clear 

 glass front of the cylinder or bottle. In these cases I 

 always classified the pupae as " orange through glass " or 

 as "orange on glass," the pupae in the latter case being 

 often not near the special colour, although the larvae in 

 moving about had probably been at times exposed to the 

 colour influence. If, however, these larvae follow the same 

 laws as those of Va7iessa urtic^, they are only sensitive when 



