448 Mr. 'B oulion's further experiments upon 



From the occasional occurrence of dark brown patches 

 on a h'ght brown cocoon, it is probable that the larva 

 stains the completed structure, in the manner described 

 by Mr. Bateson. 



Pcecilocamjm pnjwli 1891. — Four cocoons were spun 

 amonp; leaves and twigs of Quercus ccrris ,- these were 

 quite black on all exposed parts, while two spun between 

 pieces of white paper were not nearly so dark. The 

 blackness is, however, due to something which is not 

 silk, the latter being of a much lighter brown. It pro- 

 bably comes from the digestive tract (for neither the 

 paper nor the leaves or twigs around the cocoons appeared 

 to be gnawed), and has the appearance of bitten up 

 food or faeces. It will be interesting to ascertain accu- 

 rately what this substance is and why the larva has 

 so much less of it when the cocoon is constructed in 

 the paper. It may only follow from an accidental 

 separation from food just before maturity, or from dis- 

 turbance. Under any circumstances, there seems to be 

 no question of colour adjustment, for the larvae in the 

 paper made the most conscientious use of all the 

 material they had, and spread it out so as to cover 

 the exposed part of their cocoons as completely as 

 possible. 



Halias prasinana 1892. — I brought forward H. prasi- 

 nana as an example of this power of colour-adjustment 

 in 1887 (Proc. Ent. Soc, pp. 1, li). When Mr. Bateson 

 had shown a source of error in interpretation, owing to 

 the effect of disturbance on the larvae, I felt that this 

 case could no longer be sustained without further experi- 

 ment, in which such errors were specially guarded 

 against. I have fortunately been able to make a few 

 such experiments during the past autumn, which, 

 so far as they go, entirely support my earlier conclu- 

 sions. 



A few nearly mature larvae, beaten by Mr. Arthur 

 Sidgwick and myself, were placed, directly after capture, 

 in two cylinders. A twig of oak bearing leaves was 

 placed in each of these, and each of them stood on a 

 perforated plate and had a muslin top. The space around 

 the oak twig was filled in one cylinder with white paper 

 spills, in the other with dark sticks, chiefly of Quercus 

 cerris. After this the larvae were not touched, and it is 

 clear that there is no reason for assuming that the 



