440 MR, E. B. POULTON ON THE COLOUR-RELATION BETWEEN EXPOSED 
when they are examined as transparent objects; hence the amount of 
opaque pigment in the lighter figure (9) is very small indeed. 
Figs. 10 and 11, both X 7, represent respectively the cuticle of the left pupal fore¬ 
wings of a green and a grey variety of Vanessa Io. There is seen to be an 
immense difference in the ground-colour as well as in the amount of 
black pigment. The dark networks seen in these and the two last figures 
are purely cuticular in position, and were all drawn from the empty pupa- 
cases from which the imagines had emerged. The dentated outline within 
the margin of all the fore-wings, and especially distinct in fig. 11, 
corresponds to the shape of the imaginal wing which was developed 
under this part of the pupal wing. In correspondence with this fact, the 
pupal pigments are altered over the area where the imaginal wing will 
develope. The pigmented lines indicating the nervures of the imaginal 
wing really stop short at the dentated margin, but they are prolonged 
beyond as irregular lines of pigment which produce the deceptive 
appearance of uninterrupted continuity. It was necessary to describe 
the appearance thus far, but it is a subject upon which I am now at work. 
The object of the figures is to give a representation of the relative 
amounts of cuticular pigment, and not to reproduce morphological 
features (viz., the venation, &c.) with exactness. 
Figs. 12 and 13, both X 2, represent respectively a dark and a. light gdded pupa of 
Vanessa atalanta. Although the golden appearance is so much less 
diffused than in V. urticce, it is especially brilliant on the places where 
it- does occur. These two varieties were respectively obtained by the use 
of dark and gilt surroundings. 
Figs. 14 and 15, both natural size, represent respectively a green and a brown 
variety of the pupa of Papilio machaon. The green variety was 
obtained in brown surroundings, and the brown variety in green 
surroundings, and they are figured so as to indicate this relationship. 
Thus the species is obviously unaffected by the colour of its surroundings. 
Figs. 16—21, inclusive, represent the colours made use of in experimenting with the 
larvae of the Pieridae. Fig. 16 = dark red; 17 = deep orange; 18 = pale 
yellow ; 19 = green tissue - paper ; 20 = pale bluish - green ; 21 = dark 
blue. 
Figs. 22 and 23. Natural size. The brown and green forms of the dimorphic pupa of 
Eyhyra omicronaria. The colour of these pupae follows that of the 
respective larvae, and is unaffected by surrounding colours. 
Figs. 24-30, inclusive, all X 2, represent types of the different varieties of the 
pupae of Pieris brassicce obtained in the experiments. Fig. 24 represents 
the darkest variety, called (1), a, the ground-colour being of a greyish- 
orange ; the less dark, fig. 25, represents a greyish-green, (l), (3. Fig. 26 
