LEPIDOPTEROUS PUP^E AND THEIR SURROUNDING SURFACES. 
403 
(3.) The last pupa, was found September 16 at Seaview (Isle of Wight) on a nettle- 
bed from which all the larvse had disappeared, but upon which an evidently large com¬ 
pany had been. The pupa was an exceptionally golden (3), but nevertheless it was dark 
in the parts which were not golden. The pupa looked unhealthy and did not undergo 
development; in the winter it had evidently been dead for a long time, and, breaking 
it in two, I found that it was completely filled with the larvse of Ichneumon flies. 
Hence the only exceptions I was able to find are readily explicable : they were all 
diseased, and doubtless the process of pupation was hurried on by their abnormal 
condition. 
But, while it seems thus probable that the biological value of the gilded appearance 
was primarily due to its resemblance to glittering mineral surroundings, it is almost 
certain that in the course of time it has come to be used for other purposes. The 
most obvious of these is that it may act as a “ warning ” colour, indicating the 
possession of unpleasant qualities (taste or smell). But that this cannot be the 
original use is, I think, shown by the following considerations:—(1) The extreme 
specialisation of the means by which the colour is produced, and the fact that it is 
probably less effective than the crude combinations and startling contrasts of pigment 
colours upon which other warning colours depend; furthermore, belonging to such a 
very different type of colour, it does not follow the principle of a general resemblance 
between the various warning colours, which offers to insect-eating vertebrates as short 
and easy an educational career as possible. (2) The fact of the colour-relation itself, 
in which these gilded appearances have been shown to play a very important part. 
Now an adjustable colour-relation is the very highest and most complete means 
by which protective resemblance to surroundings can be produced, taking cognisance, 
as it does, of the inevitable differences between the surroundings of different 
individuals. But the object of a warning colour is to render its possessor as unlike its 
surroundings as possible, and hence it is something very essentially distinct from a 
colour which causes it to resemble its surroundings in the most perfect of all ways.* 
Nevertheless there is nothing to prevent the one from changing into the other in 
the course of time. And the present condition of any animal is such a compound 
phenomenon, made up of so many modified and unmodified habits and structures 
connected with other older modes of life, interwoven with those which are especially 
related to its present needs, that it would not be surprising to find that a pupa 
which made use of the gilded appearance as a warning, in order to render it con¬ 
spicuous, nevertheless retained something of the ancestral significance of the 
appearance in responding to some unusual stimulus caused by gilded surroundings. 
This suggestion is supported by the case of Acrcea esebria, alluded to below. 
* Since the above was written I have tested the golden pupae of V. urticce by offering’ them to insect- 
eating animals. There is, evidently, nothing distasteful about them, for the most scrupulous of all 
insect-eaters yet tested—a Marmoset—ate them readily one after the other. They were also freely 
eaten by insectivorous Birds. The experiments strongly sxipport the view that the gilded appearance is 
of protective significance.—Sept. 9, 1887. E. B. P. 
3 F 2 
