36 Experimental Zoology 
mentation of the caterpillar and of the adult. The caterpillar 
of the death’s head moth (Acherontia atropos) is ordinarily 
yellow, but has also a black type. Dasychira pudibanda is 
white, but has a green and gray variety, etc. 
The color of many caterpillars is much influenced by the 
food in the digestive tract that can be seen through the semi- 
transparent skin. Poulton has also shown that certain of the 
epidermal pigments are derived from the chlorophyll absorbed 
with the food. He separated into three groups caterpillars of 
Agrotis pronuba: the first was fed with the green leaves of 
cabbage, the second with the yellow etiolated leaves. Both 
lots developed their normal yellow-brown color. A third group 
was fed on leaves deprived of the green and of the yellow 
coloring matter, and only the brown pigments developed. 
Standfuss has produced within a few hours color changes 
in the caterpillar of Eupithecia absinthiata. It becomes ‘‘a 
lemon-yellow when fed on the yellow bunches of Solidago, 
green on non-flowering leaves of the same plant, rose on the 
‘buttons’ of Statice armeria, white on the umbels of Pimpinella 
saxifraga, brown on the bouquets of Artemisia vulgaris, and a 
delicate blue on the small balls of Succisa pratensis.” Similar 
results are known for other forms. Pictet finds also that the 
colors in certain caterpillars that hibernate tend to disappear, 
but reappear again a few days after feeding begins again in the 
spring. The colors of some species change with each moult. 
Difference in the color, and even in the markings of caterpillars, 
occur when they are fed on food other than the normal. In 
some cases the effect is direct, as explained above; in other 
cases the effects are indirect, i.e. not due to the food in the 
digestive tract or to the pigments directly absorbed and present 
in the skin or in the blood. In the case of Ocneria dispar the 
food plants that produce lighter colors in the moths have the 
same effects on the caterpillar. Similarly for the dark or mel- 
anistic changes. Moreover, the effects may last over for one 
or two generations after the caterpillar is again fed on its 
normal food. 
