402 
MR. E. B. POULTON ON THE COLOUR-RELATION BETWEEN EXPOSED 
having wandered from the food-plant, and under these circumstances it makes no 
attempt at concealment, but hangs freely suspended against a background with which 
it harmonises in colour. The contrast between the larval habits when it selects 
vegetal or mineral surroundings for pupation suggests very strongly that its resem¬ 
blance to the latter is ancestral, while its somewhat laborious adaptation to the 
former has been far more recently acquired. V. urticce, however, has no green form 
like V. Io, and has not the protective habit of V. atalanta, and I find that in Nature 
it exhibits the strongest disinclination to pupate on the food-plant. In confinement 
this is also true if it be provided with a surface up which it can readily climb, but the 
commonest cages are made of glass, which is ascended with difficulty and after foot¬ 
hold has been ensured by spinning a silken surface over the glass. In spite of this, 
the vast majority of larvae do ascend the glass sides, and become suspended from the 
roof. I must also add that the late Mr. Edward Newman states of this larva 
(‘ British Butterflies,’ p. 53) that it prefers for pupation the underside of a nettle-leaf 
to other situations which he describes as sometimes selected. I can only say of this 
statement that it is entirely contrary to my experience. It is possible that Mr. 
Newman’s opinion may have been partially or entirely derived from watching the 
larvae in confinement. Among the 13 series of larvae of this species, described above, 
it will be found that many were only the scanty remnants of companies, and in nearly 
all these cases I had previously seen the larvae, and knew that the companies were 
large. I made it a practice to leave the larvae on their food-plant as long as possible, in 
order to save the trouble of rearing them, and to ensure healthy pupae. In this way, 
by miscalculating the time at which they would become adult by some hours, I often 
came in time to find only a few larvae remaining, all the others having wandered away 
in search of a surface on which to pupate. Being very anxious for all the material I 
could get, I always searched the nettle-beds most carefully, and if any larvae had been 
suspended, or had pupated on the food-plant, they would almost certainly have been 
detected. But throughout the whole of the season I only found three pupae in this 
position, and no suspended larvae, although it would be easy to calculate the number 
of larvae which had pupated ; when I searched their food-plant there must have been 
very many hundreds. And the history of these three pupae is important. 
(1.) Wats found August 22, 1886, on the large nettle-bed near South Hincksey, on 
which portions of two companies of larvae were found on the same daty. The pupa 
was a very brilliant (5), but the lustre was silvery rather than golden, and the pupa 
looked unhealthy. About September 12 numbers of small Ichneumon files emerged 
from the pupa case. Mr. E. A. Fitch kindly named the species for me ; it was 
Pteromalus puparum, a common parasite of the Yanessidse. 
(2.) August 31, another pupa was found on the same nettle-bed near South 
Hincksey, but it was empty and perforated by the Ichneumon flies, which had already- 
escaped. It had evidently been very golden and probably like the last. 
