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. Cu^not. 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 Cu^not found that throughout 



