314 MR. E. B. POULT ON ON THE COLOUR-RELATION BETWEEN EXPOSED 
surroundings. Furthermore, it will be shown that the colour-relation is due to larval 
o 
susceptibility during very many hours before pupation, so that, unless special precau¬ 
tions are taken, the larvae may be disturbed or removed from one surface to another in 
feeding, observing, &c., and the results are likely to be highly irregular, for the boxes 
would always contain one colour which acts powerfully upon these two species, i.e., 
the green leaves of the food-plant. 
Professor Meldola, in a paper communicated to the Zoological Society (“ On a 
certain Class of Cases of variable Protective Colouring in Insects,” ‘ Zool. Soc. Proc.,’ 
1873, p. 153) confirms Mr. T. W. Wood’s observations on the pupae of the Pieridae, 
for he states (p. 156), “I have observed a similar fact with respect to the pupae of 
Synchloe ( Pieris) brcissicce and S. rapes, specimens from a black fence being generally 
darker than those found on walls.” Professor Meldola informs me that this con¬ 
clusion was obtained from the comparison of large numbers of individuals. 
The next observation of the correspondence between the colours of variable pupae 
and that of their surroundings is found in a paper by Mrs. M. E. Barber, communi¬ 
cated by Mr. Darwin to the Entomological Society of London (‘Entom. Soc. Trans.,’ 
1874, p. 519). Mrs. Barber had experimented with the pupae of Papilio nireus, 
common in most parts of the Cape Colony. The larva itself in this species has also 
the power of colour adaptation to its surroundings, for Mrs. Barber states that it 
is dark-green when found feeding upon orange trees, and lighter green upon Vepris 
lanceolata. In the natural state the pupal colours are always similar to those of the 
leaves of the food-plant, when pupation takes place among the leafy twigs—its usual 
surroundings. In Mrs. Barber’s experiment the larvse were reared “ in a case with 
a glass cover ; the case was partly made of wood and partly of brick : the colour of the 
wood was a dullish yellow, that of the brick a purplish-brown." Orange leaves, on 
which the larvse fed, were placed in the case, and also a branch of the common bottle¬ 
brush shrub, of which the dead leaves were pale-green. Of the resulting pupae some 
were fixed to the orange leaves, and were of the usual deep-green colour, like that 
of the surrounding leaves ; others were fixed “ to the bottle-brush branch, and these 
became pale yellowish-green pupae of precisely the same colour as the half-dried leaves. 
One of the caterpillars in particular affixed itself upon the wooden framework of the 
case, where the wood and the brick came in contact with each other, and to my 
surprise this caterpillar, after throwing off its bright-green skin, assumed the colours 
of both the wood and the brick, its under-side resembling that of the wood to which 
it was attached, and the upper side that of the adjacent brickwork.” 
“ Some days later another specimen affixed itself to the wooden frame of the case, 
and then became a yellowish pupa of the same colour as the wooden frame.” 
Mrs. Barber then tried the effect of surrounding a caterpillar before pupation with 
scarlet cloth, but the resulting pupa was of the common deep-green form, in which, 
however, the coloured spots usually present in this variety were of a brighter red. 
Mrs. Barber suggests that these correspondences of colour may be analogous to those 
