438 
MR. E. B. POULTON ON THE COLOUR-RELATION BETWEEN EXPOSED 
for the experiment was not carried out in the best way : there was not a sufficient 
quantity of both colours in the surroundings. 
Dr. Wilhelm Muller, of Greifswald, refers to the above account, and evidently 
regards the Ephyridse as peculiar in this respect. His evidence is all the more valuable 
because of his careful work on larvae and pupae of Lepidoptera during many years spent 
in South America. He says (“ Stidamerikanische Nymphalidenraupen,” Spengel, 
‘ Zoologische Jahrbucher/ vol. 1, Jena, 1886, p. 234) :—“ Eine riihmliche Ausnahme 
machte E. B. Poulton, welcher feststellt, dass sich bei verschiedenen Species der 
Gattung Ephyra der Dimorphismus der Raupe bei der Puppe erhalt, so dass helle 
Raupen nur helle Puppen, dunkle Raupen nur dunkle Puppen liefern.” The colours 
of the pupae being predetermined, and following rigidly the colours of the respective 
larvae, it follows that these organisms afford an interesting contrast to all the other 
species of exposed pupae described in this paper (for there is no colour-relation between 
the larvae and pupae in Papilio mackaon, &c.), while special protective resemblances in 
the pupae seem to be only possible as the results of the selection of appropriate 
colours upon which to pupate. In the above-recorded observations there was quite 
insufficient evidence to support the theory that the larvae have any such power, but I 
do not think that they are by any means conclusive in the other direction. 
Summary. 
The results of this paper may be shortly summarised as follows :— 
1. The following exposed pupae of the Rhopalocera have been proved in this paper 
to possess an adjustable colour-relation to their surroundings —Vanessa Io, V. urticce, 
V. atalanta, Piens brassicce, and P. rapes. The relation had been previously proved 
for some of these species, and for others, which I have not had an opportunity of 
investigating, e.g., Papilio vireu.s and P. demoleus. 
2. On the other hand, dimorphic pupae which are closely allied to the sensitive 
forms may be uninfluenced by surrounding colours, e.g., Papilio machaon and 
P. poly damns. In the genus Ephyra (ITeterocera) the dimorphic pupae are quite 
uninliuenced by their surroundings, the pupal colours corresponding to those of the 
dimorphic larvae. 
3. The previously accepted theory, which explained the pupal colour-relation as 
following from the action of light upon the moist skin of the freshly-formed organism, 
is entirely disproved, and it is shown that the influence works upon the larva during 
the period which intervenes between the cessation of feeding and pupation. 
4. This intervening period was carefully investigated in V. urtiece, and it was found 
that, after ceasing to feed, the larvae wander for a variable time, then rest for about 
15 hours upon the surface selected for pupation, and finally hang suspended, head 
do wnwards, for about 18 hours, after which time pupation takes place. By transferring 
