VII 
THE COLOURS OF THE LEPIDOPTERA 
159 
Contrast between Pigments of Butterflies 
and Caterpillars 
We have already considered some of the 
characters of the caterpillar—how it eats far in 
excess of its immediate requirements, how it is rela¬ 
tively sluggish, and remarkable for its rapid growth. 
There comes a period, however, when the caterpillar 
ceases to eat, ceases to grow, becomes absolutely 
sedentary, and passes into the pupa stage. Here 
within its pupal covering fundamental changes take 
place ; there is first an extraordinarily thoroughgoing 
destruction of tissue and then an equally thorough¬ 
going reconstruction. Now if we turn to higher 
forms whose physiology is well known, we find that 
such extensive changes in tissues are associated with 
a large and increased production of nitrogenous waste 
products. It is natural to conclude that this also 
occurs in the pupa. The butterfly is built up by 
the aid of the reserves stored by the caterpillar, 
but in the course of the reconstruction there must 
be an enormous production of waste substances. 
Unfortunately we know relatively little of the 
physiology of insects, but there is at least one 
interesting research by M. L. Cuenot. This 
naturalist worked at the Orthoptera and found 
that besides the Malpighian tubes, the familiar 
excretory organs of insects, certain cells of the 
fatty body stored up waste products. In the 
Orthoptera — cockroaches, locusts, grasshoppers, 
etc.—waste products are apparently not employed 
in coloration ; and Cuenot found that throughout 
