146 COLOUR IN NATURE chap. 



the two processes would be very closely analogous. 

 According to this theory, food containing Hpochrome 

 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 Hpochrome 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 



