414 MR. E. B. POULTON ON THE COLOUR-RELATION BETWEEN EXPOSED 
This analysis seems to prove almost conclusively that the stronger illumination 
increases the influence of the black surface upon the larvse. At the same time, it must 
be remembered that A. and B. were larvae which had been kept for some time in the 
cylinders, whereas C., D., and E. had been under more normal conditions, as the 
pupae were found wild. 
The relation of the effect of black surfaces to those of other colours will be shown 
later in an analysis of the colours of all pupae which had been exposed to such 
surroundings during the whole of the preparatory period. 
II. White. 
A. In almost complete darkness. 
On September 9 a large number of mature larvae of P. brassicce and a few 
of P. rapce were placed in a light-blue cardboard box, of which the internal 
surface was white. (The length was 3 decimetres, width IT decimetre, and the 
depth 7'7 centimetres.) The cardboard was thick and opaque, so that light could 
only enter to a slight extent between the lid and the box, and perhaps at the angles. 
The larvae were thus exposed to a white surface in almost complete darkness. No 
notes were taken as to the times of pupation, &c. 
Results. —When the comparison took place there were 41 living pupae of P. brassicce , 
and, of these, 20 were fixed to the roof, being greatly crowded in an irregular group 
1 decimetre long and 7 centimetres in its greatest width. 
Of these 20 pup*.4 were (1), a, very dark indeed ; 3 being very 
faintly orange, and 1 almost entirely 
grey, but slightly greenish. 
14 „ (1), ft, 5 being faintly orange, and the others 
more or less yellowish-green, but 
the grey tints predominant in all. 
2 ,, ( 1 ), 7 , the ground-colour yellowish-green, 
mottled with deeper green. Black 
patches small. 
2 pup* were fixed to the roof close 
together, but at a distance from 
those described above. 1 was ( 1 ), ft, faintly orange. 
1 ,, ( 1 ), 7 , distinctly greenish and less grey than 
usual; the black patches rather 
more developed than usual. 
1 pupa was isolated on the roof, and was ( 1 ), 7 , yellowish, mottled with greenish; 
typical. 
3 pupae had been previously taken off 
the roof, or had fallen off it; position 
unknown. 2 were ( 1 ), ft, pale greyish-orange ground-colour; 
1 of them with a rather deeper tint, 
and mottled with greenish. 
1 was ( 1 ), 7 , greyish-green; typical black patches. 
