430 On the Colours of certain Lepidopterous Larvae. 



the larvae are fed upon leaves without chlorophyll or etiolin. But 

 over the general surface of the body the cuticle is very thin, and 

 only contains the black spots and patches of true pigment, while the 

 brown or green ground colour, derived from plant pigments, is siib- 

 cuticular in position. Hence in a larva fed on pigmentless parts of 

 leaves, represented in fig. 3, this latter ground colour is replaced by 

 a creamy tint which is due to the uncoloured tissues of the body, 

 especially the fat, and to the contents of the digestive tract. This 

 creamy ground colour, combined with the spots of true pigment in 

 the cuticle, produces the general greyish appearance of these larvae. 



The posterior segments of the larva, painted at the same date, 

 X 4 diameters, are also represented in the figure, indicating that the 

 thickened cuticle of the supra-anal plate (which possessed a sharper 

 outline than that represented in the figure) contains both brown 

 ground colour and black spots of true pigment, while the general 

 surface presents the combination of a white ground colour and dark 

 spots, conferring a grey appearance. 



