LEPIDOPTEROUS PUP/E AND THEIR SURROUNDING SURFACES. 
409 
Both species are peculiarly adapted for experiments of this kind because of their quiet 
disposition and the great length of the period preparatory to pupation. 
Before describing and classifying the results of the experiments upon the larvae of 
P. brassiere, it is necessary to construct a standard of the various degrees of colour 
assumed by the pupae. In making such a list, it is necessary to take account of two 
features, each of which varies—the ground-colour, and the pigment patches and spots 
which are visible to the naked eye. Seven of the principal varieties are figured in 
Plate 26, figs. 24—30, all X 2. 
(1) The normal form. In these pupae the ground-colour is always more or less 
greyish from the abundance and relative size of minute black pigment spots which 
occupy depressions in the cuticle. They can often be distinguished with the naked eye 
on close and careful inspection ; but th P ir general effect is to produce the greyish 
appearance. The large black pigment patches and spots are nearly always abundant, 
and when the ground-colour is darkest the former also contribute towards a dark 
appearance by their especial size and number. The ground-colour may be of various 
tints —greyish-green, orange, yellow, or a peculiarly opaque-looking greyish-white. The 
amount of the grey colour always present subdues the differences between these tints, 
so that they resemble each other far more than the above description would seem to 
imply. The wings and under-side are always lighter than the rest of the surface, 
especially as regards the ground-colour, for the pigment patches are often very pro¬ 
nounced in these parts of the pupa. The following subdivisions are well marked, 
although transitional varieties occur :— 
(a) The darkest forms with greyish-green, orange, yellow, or white ground-colour. 
(/3) Intermediate forms, with lighter ground-colour of the same tints, and smaller 
and fewer pigment patches. 
(y) The lightest of these forms, with ground-colour still greyish, but the pigment 
patches very small relatively to (a) or (/3). 
(2) The last subdivision passes into this variety, in which the ground-colour is 
an opaque-looking whitish-yellow, often with greenish areas on part of the surface, 
the pigment patches being very small. The greyish hue is lost because of the minute 
size of the dots in the ground-colour. Hence the effect is very light. The wings 
and under-side are lightest, and not so opaque as the dorsal and lateral surfaces; the 
pigment spots in these parts are small, 
(3) A still more abnormal, very well-marked, variety, possesses a deep transparent¬ 
looking bluish-green ground-colour, in which the minute dots and the large patches 
are even less developed than in the last degree. An opaque whitish-yellow band, 
like the ground-colour in (2), occupies the anterior half of that part of the third 
abdominal segment which is seen dorsally, and extends on to the posterior part of the 
segment in front; and the dorsal surfaces of the abdominal segments behind the third 
are often mottled with the same colour. The median dorsal ridge is strongly marked 
in orange, interrupted in the abdominal region by opaque greenish-white, and the 
MDCCCLXXXV1I.—B. 3 G 
