[ ;m ] 
XLV. An Enquiry into the Cause and Extent of a Special Colour-relation between 
certain exposed Lepidopterous Pupae and the Surfaces which immediately sur¬ 
round them. 
By Edward B. Poulton, M.A., F.L.S. 
Communicated by Professor E. R ay Lank ester, F.R.S. 
Received and R.ead, February 10, 1887. 
[Plate 26 .] 
Contents. 
Introductory. 311 
Historical. 312 
Previously accepted explanations. 317 
Experiments upon Vanessa Io . 317 
Experiments upon Vanessa urticce . 319 
Experiments upon Vanessa atalanta . 398 
The biological value of the gilded appearance in pupae. 399 
Experiments upon Papilio machaon . 406 
Experiments upon Pieris brassicce and P. rapce . 408 
Observations upon the colours of the pupae in the genus PJphyra . 437 
Summary. 438 
Description of Plate. 439 
In troductory. 
The present investigation grew out of the enquiry into the colour-relation between 
Lepidopterous larvae and their food-plants. In the search for the larval sense-organ 
which is affected by the light reflected from surrounding surfaces, great difficulty was 
experienced from the fact that the influences work slowly through the whole of larval 
life. Thus the ocelli must be eliminated by blinding five times in the life of each 
caterpillar, and there is always the chance of the skin being thrown off a little earlier 
than usual, in which case the success of the whole experiment might be endangered, 
for the coverings of the eyes are changed with the rest of the skin. It seemed 
probable that in the pupal colour-relation the influence must act during a short and 
rigidly limited time, in which experiments could be conducted with much hope of a 
successful isolation of the effective sense organs. 
14 11.87 
