LEPIDOPTEROUS PUP^l AND THEIR SURROUNDING SURFACES. 
435 
II. Bloch and white during Stage III .—September 16 , a small group of larvm of 
P. hrassicce were girdled upon a clear glass sheet which formed the covering of an 
ordinary wooden box. Other larvm and freshly-formed pupae fell down from the 
same sheet, and will be described below’ (HI-). A sheet of white paper was fixed 
under half of the group and a black sheet under the other half, and a shelf was 
fixed between the two colours, covered with w'hite paper towards the white side and 
black towards the black side, and the whole was placed vertically in a strong north¬ 
east light, close to the window. Thus the two groups of larvae were exposed to black 
and white respectively during the remainder of Stage III., and there was reason to 
believe that the stage had not long begun. Notes wrnre taken as follows :— 
Sept. 16, 7 p.m. 
Experiment began, the paper and shelf 
having been fixed. 
„ 17, 7.20 p.m. 
1 larva on the white area has only just 
pupated 
24 hours on white; thus Stage III. 
longer than this period of time. 
It is a (2), opaque greenish-white, 
rather yellow anteriorly ; normal. 
,, 18, 8.30 a.m. 
Another larva on the white area has 
pupated a few hours 
And 3 larvae on the black area have 
pupated a few hours 
And 1 larva on the black area was now 
pupating 
It is a (2), opaque greenish-white, 
lighter than the above, and smaller 
black spots. 
2 alive, and both intermediate between 
( 1 ), 7 , and ( 2 ), because of the amount 
of grey dusting; very small black 
patches. 
Dead. Stage III. at least 37^ hours. 
,, 18,11.40 a.m. 
The last larva on the black has pupated 
Dead. Stage ill. longer than 37lr hours. 
It thus appears that the pupae were slightly affected by the white and black 
surfaces, although to a very small extent. Stage III. may have been somewhat 
protracted in consequence of the glass being turned in such a position that the larvae 
were head downwards, an attitude never assumed in this species before pupation. 
III. Black and white during Stage III. —At 7.30 p.m. , September 16, six moist and 
freshly-formed pupae and seven girdled larvae of P. hrassicce (alluded to above) fell 
down from a clear glass sheet to which they had been suspended (being the covering of 
an ordinary wooden box), owing to the continuous silken web which they had spun 
becoming detached from the glass. This was thought to be an opportunity of testing 
the sensitiveness of the pupa to coloured surroundings (as opposed to the larva), and 
therefore the pupae and larvae were each divided into two groups, and were placed on 
a black and a white surface. By 7.5 p.m., September 17, six of the larvae had pupated, 
and the seventh pupated at 9.15 p.m. on the same evening. 
Residts .—Seven pupae were living which had been exposed to the black surface : 
Of these, 4 were (1), ft, 3 yellowish-green, but very grey ; 1 greenish. 
3 ,, (1), y, ground-colour opaque whitish-yellow, almost like (2), hut with larger black 
patches than in this degree, and even more developed than is usual in ( 1 ), 7 . 
3 K 2 
