252 Experiments upon the colour-relation, ce. 
** Stage II., in which the larva rests motionless upon 
the selected surface, and towards the end of the stage 
spins the boss of silk for its subsequent suspension ”’ 
(Vanessa). The only variation in the case of Pieris 
being that it proceeds to spin first a slight web for 
attachment, and then adds the silken anal support and 
girdle whilst in this stage. 
“ Stage III., in which the larva (Vanessa) hangs 
suspended by its posterior claspers from a boss of silk;”’ 
or in Pieris, in which it remains girdled in a passive 
state until the ecdysis takes place, and it becomes 
a pupa.* 
With regard to the duration of these stages in Vanessa 
urtice, Mr. Poulton found that Stage I. is variable, 
depending upon the relative proximity of surfaces suit- 
able for pupation ; Stage II. lasts for about 15 hours; 
and Stage III. about 18 hours. The larve are sensitive 
to surrounding colours for about 20 hours preceding the 
last 12 hours of the whole period. 
In regard to these stages, the conclusions arrived at 
by Mr. Poulton, after many elaborate and extensive 
observations on the point, is that ‘‘ Stage II. is the time 
of chief susceptibility to surrounding influences,” and 
that ‘‘ the larva can hardly be susceptible after the first 
part of Stage III.” + 
_Although Mr. Griffiths was unaware of the special 
interest attaching to the period before pupation, and 
therefore neglected to take any notes, the general con- 
clusions contained in Mr. Poulton’s statement, which I 
have just quoted in abstract, are fully borne out by Mr. 
Griffiths’ results, which are indeed incapable of any 
explanation otherwise. It is, therefore, much to be 
* Loc. cit., pp. 827, 328. 
} Ibid., p. 540. On p. 860 Mr. Poulton further observes, 
respecting Stage III., that, ‘‘ although this stage is, asa rule, so 
much longer than any other, the larval sensory surfaces are 
probably only in a condition to be influenced in its most early 
part, for very rapid changes of pupal construction and shape are 
going on beneath the surface. These would seem to preclude the 
possibility of an external shell, shortly to be cast off, having any 
important physiological relation with the organism beneath. But 
in Stage II. the larva retains its shape, and the whole of its 
surface is in close relation with the colour into correspondence 
with which the pupal tints will afterwards deepen.” See also 
p. 892 of Mr. Poulton’s paper. 
