326 
MR. E. B. POULTON ON THE COLOUR-RELATION BETWEEN EXPOSED 
August 19. Of these, two were dead and discoloured, one was on the roof, and two 
on the food-plant. 
Of the 2 on the food-plant . . 1 was (2). 
1 „ (3). 
The 1 on the roof. ,, (5) typical. 
These pupae are certainly darker, as a whole, than the unblinded ones, but the 
difference is not great enough to suggest the blinding as a necessary cause, while 
other experiments (to follow) clearly show that it cannot have been effective in this 
way. 
This concludes the experiments conducted upon the larvae of Series II., kindly sent 
me by Mr. Pode. The great mortality was due to the fact that the larvae were sent 
very young, and were thus brought up for nearly the whole period of larval life in 
unnatural conditions. In the following experiments I made use of larvae which were 
found in various localities near Oxford, and which were allowed to remain upon the 
nettle-bed until they were nearly mature. In this way I secured a very high 
percentage of pupae. Nevertheless, in the experiments just recorded (II.), that 
insight into the colour sensitiveness of the species was gained which rendered all the 
following experiments possible and suggested the various modifications and details. 
III.—A company of mature larva) was found August 15 beside the towing-path of 
the “ Upper River/’ near Oxford. In the press of other work they were in some cases 
temporarily placed in short, wide, glass cylinders, covered with sheets of glass, until the 
night of August 16, when they were counted and to some extent re-arranged, but in 
the meantime they had ceased to feed ; in fact, the great majority did not eat anything 
at all after capture. They were arranged as follows, and were all compared August 21, 
both together and with those of Series II. 
A. A clear glass cylinder was employed, 2'07 decimetres in internal diameter and 
7‘0 centimetres in height. This was placed upon a floor of white paper, upon 
which a small quantity of the food-plant was lying horizontally, and the cylinder 
was covered with a sheet of white translucent “ opal ” glass, forming the roof. The 
larva) described in this division, although first counted and noted on the night of 
August 16, had previously been in the same cylinder with the same white roof 
(although without the paper floor, as the cylinder merely rested on the ordinary floor 
boarding of the room). On the night of the 16tli they were placed on a table about 
six feet from a very large window, so as to be exposed to a good east light during the 
day. Before this time they had been upon the floor of the room under the shadow of 
the table. When re-arranged on the 16th, 11 larvae were hanging from the roof 
preparatory to pupation, and by 4 p.m. on the 17th four had pupated and were 
removed, and by the same evening seven more had also changed. When compared on 
August 21st, there were 15 pupae arranged and coloured as follows :— 
