COLOR AND COLORATION 1 97 



kn<\vn as nrticoides. Food affects the color of the larva also, 

 as Poulton found in the case of caterpillars of Tryphcena pro- 

 niibu, all from the same batch of eggs. When fed with only 

 tin 1 white midribs of cabbage leaves, the larvae 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 larvae 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 promcthea, Leptinotarsa decem- 

 Hucata (Colorado potato beetle), Coccinellidse (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 

 Dcilephila lincata. 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 Annrida 

 inaritiina 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 larvae 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 



