COLOR AND COLORATION 197 
known as urticoides. Food affects the color of the larva also, 
as Poulton found in the case of caterpillars of Tryphena pro- 
nuba, all from the same batch of eggs. When fed with only 
the white midribs of cabbage leaves, the larvee remained almost 
white for a time, but afterward showed a moderate amount of 
black pigment; when fed with the yellow etiolated heart-leaves 
or the dark green external leaves, however, the larvee all be- 
came bright green or brown—the same pigment being derived 
indifferently from etiolin (probably the same substance as 
xanthophyll) or chlorophyll. 
Though the pigments may differ in color or amount accord- 
ing to the kind of food, the color patterns vary without regard 
to food. Thus Callosamia promethea, Leptinotarsa decem- 
lineata (Colorado potato beetle), Coccinellidee (lady-bird 
beetles) and a host of other insects exhibit extensive individ- 
ual variations in coloration under precisely the same food con- 
ditions. Caterpillars of the same kind and age are often very 
differently marked when feeding upon the same plant; for 
example, Heliothis armiger (corn worm) and the sphingid 
Deilephila lineata. Furthermore, striking changes of colora- 
tion accompany each moult in most caterpillars, but particu- 
larly those of butterflies, and these changes may prove to have 
an important phylogenetic significance. Individual differ- 
ences of coloration apart from those due to the direct action 
of food, light, temperature and other environmental condi- 
tions are to be explained by heredity. 
Effects of Light and Darkness.—Sunlight is an important 
factor in the development of most animal pigments, as they 
will not develop in its absence. The collembolan Anurida 
maritima is white at hatching, but soon becomes indigo blue, 
unless shielded from sunlight, in which event it remains white 
until exposed to the sunlight, when it assumes the blue color. 
Subterranean or wood-boring larvee are commonly white or 
yellow, but never highly colored. ‘The most notable instances, 
however, are furnished by cave insects. These, like other 
cavernicolous animals, are characteristically white or pale 
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