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COLOR AND COLORATION 177 



lineata. Furthermore, striking changes of coloration accompany each 

 molt in most caterpillars, but particularly those of butterflies, and 

 these changes may prove to have an important phylogenetic signifi- 

 cance. Individual differences of coloration apart from those due to the 

 direct action of food, light, temperature and other environmental 

 conditions 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 Amanda 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 pr 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 cavernico- 

 lous animals, are characteristically white or pale from the absence of 

 pigment, if they live in regions of continual darkness, but have more or 

 less pigmentation in proportion respectively to the greater or less 

 amount of sunlight to which they have access. 



Curiously enough, light often hastens the destruction of pigment in 

 insects that are no longer alive, for which reason it is necessary to keep 

 cabinet specimens in the dark as much as possible. Life is evidently es- 

 sential for the sustention or renewal of the pigments. 



A chrysalis not infrequently matches its surroundings in color. This 

 phenomenon has been investigated by Poulton, who has proved that the 

 color of the chrysalis is determined largely by the prevalent color of 

 the surroundings during the last few days of larval life. Larvae of the 

 cabbage butterfly, Pieris rapce, raised upon the same food plant (all 

 other conditions being made as nearly equal as possible) produced dark 

 pupae if kept in darkness for a few days just before pupation; yellow 

 light arrested the formation of the dark pigment and gave green pupae ; 

 while light colors in general gave light-colored pupae. This color 

 resemblance is commonly assumed to be of protective value, and per- 

 haps it is. Nevertheless, it is a direct effect of light, and does not need 

 to be explained by natural selection, even though it cannot be denied 

 that natural selection may have helped in its production. 



Poulton extended his studies to the adaptive coloration of caterpillars 

 and has published the results of an extensive series of experiments which 

 prove that the colors of certain caterpillars also are directly produced by 

 the same colors in the surrounding light. Gastropacha quercifolia, which 

 always rests by day on the older wood of its food plant, was given black 



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