LEPIDOPTEROUS PUIUE AND THEIR SURROUNDING SURFACES. 
319 
Experiments upon Vanessa urticae. 
There are certain reasons why this species is peculiarly fitted for the purpose of the 
present investigation. It is exceedingly common throughout the whole of the 
summer months, and its food-plant—nettle—is abundant everywhere ; above all, the 
larvae are gregarious, living on webs when young, scattering when older, but never to 
such an extent that more than a few yards intervene between the most widely 
separated larvae. Such companies are made up of large numbers of larvae (examples 
of the numbers will be given below), and, as each of them results from the eggs laid 
by a single butterfly, it follows that in any series of experiments conducted upon the 
individuals of a company the possible errors which might follow from different 
hereditary tendencies due to different parents—of unknown, but presumably varying, 
histories in the larval state—are completely eliminated. At the same time, the 
numbers are amply sufficient to admit of the experimental investigation being varied 
and, at the same time, carried on in the most complete manner among the offspring of 
a single pair of butterflies. During the whole summer I did not meet with a single 
instance in which the larvae of one colony could be mistaken for those of another, for 
in nearly all cases each company occupied a separate clump of nettles, and in the few 
cases in which more than one occurred upon a very large nettle-bed the larvae of the 
different companies were at different stages of growth, and, furthermore, on different 
parts of the bed. In the following series of experiments the numbers III.-XIII. 
(both inclusive) correspond to eleven companies, of which the respective larvae were 
ahvays most carefully separated. 
I. —Early in the summer I began to experiment with this species. The larvae, when 
found suspended in the breeding cages, were removed, and fixed against black, white, 
and green paper, in a strong light. The larvae in all cases pupated shortly after 
transference, and there were no apparent effects wrought upon the residting pupae. 
Later investigations showed that these negative results were due to the shortness of 
the time during which the larvae had been exposed to the influence of colour. The 
experiments also proved that the moist surface of the freshly exposed pupa is not 
sensitive to colour influences. A little later, I again experimented with an orange 
background, about twelve larvae being kept for a large part of their lives in a cylinder 
lined with this colour. The pupae were all of that very common variety which will 
be represented below as degree (3), and such negative results seem to prove that the 
species is not susceptible to such surroundings. 
II. —I had asked Mr. Pode to procure some more larvae of V. Io for me, but, as 
it was too late for the species, he sent a large number of V. urticce. These consisted 
of individuals of several companies and of different ages, but in this case it was not 
considered safe to attempt to sort them. In estimating the pupal colours, it was 
