146 COLOUR IN NATURE chap. 
the two processes would be very closely analogous. 
According to this theory, food containing lipochrome 
pigment is richer diet than food without it, and leads 
to the deposition of extra reserves in the tissues and 
indirectly to additional pigmentation. The facts 
observed by Mr. Poulton that the pigments are 
frequently found associated with fat, and tend to 
occur in the connective tissues, seem to support this 
suggestion. It is also not inconsistent with the 
observed fact that the pigments remain within the 
body of the moth, and may be used in the formation 
of the eggs and so passed on to the second genera¬ 
tion. As nutrition in the butterfly is unimportant, 
there is reason to believe that the caterpillar must 
provide the nutritive substance subsequently employed 
in the formation of the yolk. Yolk is usually remark¬ 
able for the considerable amount of fat which it 
contains, and the lipochrome may be simply trans¬ 
ferred with the fat. 
Other Characters of the Coloration of 
Caterpillars 
As to the other characters of larval coloration, 
Mr. Poulton describes cases in which colourless 
bands of fat give the appearance externally of white 
stripes. It is also of interest to note that the blood 
of the larvae, when exposed to air, oxidises and 
becomes dark-coloured or black. It is possible that 
some such oxidation process accounts for the deepen¬ 
ing in tint of the true or cuticular pigment when the 
larvae are exposed to the air. 
We do not propose here to consider the question 
