LEPIDOPTEROUS PUP.E AND THEIR SURROUNDING SURFACES. 
439 
the larvae from one colour to another it was found that the colour influence works 
for about 20 hours preceding the last 12 hours of the whole period. 
5. Blinding proved that the eyes do not form the organs which are influenced, and 
it was also shown that the complex bristles do not contain a terminal organ with this 
function. Experiments with conflicting colours appeared to prove that surrounding 
colours affect the whole surface of the larval skin, although parti-coloured pupae were 
not obtained. (There is, however, some evidence for such a result in Papilio nireus.) 
6. In all cases there are certain colours which produce no effects. In the 
Vanessidse the brilliant metallic tints of the pupae can be greatly influenced by the 
presence of gilded surfaces in the environment of the larva before pupation. This 
fact appears to prove that the metallic tints are essentially protective, and probably 
subserve concealment by their resemblance to glittering minerals, such as mica. This 
theory is confirmed by observations upon the habits of certain species with gilded 
pupae. At the same time the gilded appearance has acquired another and opposite 
significance in other species, being of use in rendering the pupae conspicuous, and 
thus acting as a signal of an unpleasant taste or smell. 
7. The amount of pigment in the superficial layer of the cuticle in the pupae of 
Pieris brassicce and P. rapes appears to be influenced by the spectroscopic com¬ 
position of the light incident upon the larvae before pupation. 
Description op Plate 26. 
Figs. 1-6, inclusive ; all X 2 diameters. These figures represent a series of the pupae of 
Vanessa urticce, ranging from the darkest to the lightest and most golden 
varieties. Fig. 1, the darkest, is that represented by the degree of colour 
called (]) in the paper. Fig. 2, rather less dark, is called (2) in the 
paper. Fig. 3 represents the degree called (3). Fig. 4 represents a 
normal (4) ; while figs. 5 and 6 represent respectively the degrees of 
colour called normal (5) and exceptionally gilded (5). 
Fig. 7. Natural size. The yellowish-green and relatively gilded form of the pupa of 
Vanessa Io, obtained by the use of yellowish - green surroundings. 
Similar varieties occur on the leaves of nettle. 
Figs. 8 and 9. X 7. These figures represent the left fore-wings and the exposed part 
of the hind-wings of two pupae of Vanessa urticce, showing the relative 
amounts of black cuticular pigment present (in the superficial layer of 
the cuticle) in two different varieties. Fig. 8 represents the degree of 
colour called (2), while fig. 9 represents that called light (3). The black 
parts of the networks alone represent black opaque pigment; the less dark 
parts of the networks are not opaque, and let the light freely through 
