198 ENTOMOLOGY 
from the absence of pigment, if they live in regions of con- 
tinual darkness, but have more or less pigmentation in propor- 
tion 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 essential for the sustension 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. Larve of Pieris rape, raised 
upon the same food plant (all other conditions being made as 
nearly equal as possible) produced dark pupee if kept in dark- 
ness for a few days just before pupation; yellow light arrested 
the formation of the dark pigment and gave green pupz ; while 
light colors in general gave light-colored pupze. This color re- 
semblance is commonly assumed to be of protective value, and 
perhaps 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 twigs, reddish brown sticks, lichens, etc., to rest upon, 
and though all the larvee were from the same cluster of eggs, 
and had been fed in the same way, each larva gradually 
assumed the color or colors of its resting place, resulting in 
exquisite examples of protective resemblance, the most re- 
markable of which were those in which the larvee assumed the 
