COLOR AND COLORATION 195 
The cuticular pigments are derived, of course, from the 
underlying hypodermis cells, and these cells themselves, more- 
over, usually contain (1) colored granules or fatty drops 
which give red, yellow, orange and sometimes white or gold 
colors as seen through the skin; (2) diffused chlorophyll 
(green) or xanthophyll (yellow), taken from the food plant. 
Unlike the structural colors, which are persistent, these hypo- 
dermal colors often change after death, though less rapidly 
when the pigments are tightly enclosed, as in scales or hairs. 
Though white and green are structural colors as a rule, 
they are due to pigments in Pieridae, Lyczenidae and some 
Geometride. 
Frequently a color pattern consists partly of cuticular and 
partly of hypodermal colors, the hypodermal or sub-hypoder- 
mal color forming “a groundwork upon which the pattern is 
cut out by the cuticular color.” (Tower.) Thus in Leptino- 
tarsa decemlineata the pattern ‘is composed of a dark cutic- 
ular pigment upon a yellow hypodermal background.” 
Combination Colors.—The splendid changeable hues of 
Apatura, Euplea and other tropical butterflies depend upon 
the fact that their scales are both pigmented and striated. 
Under the microscope, certain Apatura scales are brown by 
transmitted light and violet by reflected light, and to the un- 
aided eye the color of the wing is either brown or violet, ac- 
cording as the light is received respectively from the pigment 
or from the striated surfaces of the scales. According to 
Tower, chemico-physical colors ‘which are of exceedingly 
wide occurrence, are also the most brilliant and varied of all 
those found in insects. To this class belong all metallic, iri- 
descent, pearly, and translucent colors, as well as blue, green, 
and violet in almost every case.” 
Nature of Pigments.—Some pigments are taken bodily 
from the food; others are manufactured indirectly from the 
food, and some of these are excretory products. 
The green color of many caterpillars and grasshoppers is 
due to chlorophyll, which tinges the blood and shows through 
