( H ) 



of Lepidoptera in which the colour of the silk had been 

 controlled by the use of appropriate colours in the larval 

 environment at the time of " spinning up." Mr. Poulton 

 said this colour-susceptibility had been previously proved by 

 him in 1886 in the case of Saturnia carpini, and the experi- 

 ments on the subject had been described in the Proc. Koyal 

 Society, 1887. It appeared from these experiments that the 

 cocoons were dark brown when the larvae had been placed in 

 a black bag ; white when they had been freely exposed to 

 light with white surfaces in the immediate neighbourhood. 

 Mr. Poulton stated that the other two species subjected to 

 experiment during the past season afforded confirmatory 

 results. Thus the mature larva of Eriogaster lanestris had 

 been exposed to white surroundings by the Piev. W. J. H. 

 Newman, and cream-coloured cocoons were produced in all 

 cases ; whilst two or three hundred larvae from the same 

 company spun the ordinary dark brown cocoons among the 

 leaves of the food-plant. In the latter case the green 

 surroundings appeared to act as a stimulus to the production 

 of a colour which corresponded with that which the leaves 

 would subsequently and permanently assume. Mr. Poulton 

 further stated that he had more recently exposed the larva3 

 of Halias prasinana to white surroundings, and had obtained 

 a white and a very light yellow cocoon, far lighter than the 

 lightest of those met with upon leaves. The larva which 

 spun the white cocoon had previously begun to spin a brown 

 one upon a leaf, but upon being removed to white surroundings 

 it produced white silk. 



Mr. Stainton suggested that larvae should be placed in 

 green boxes, with the view of ascertaining whether the 

 cocoons would be green. He understood that it had been 

 suggested that the cocoons formed amongst leaves became 

 brown because the larvae knew what colour the leaves would 

 ultimately become. 



Mr. Poulton, in reply, said that, so far from the larvae 

 having any choice or intelligence in the matter, he felt 

 convinced that the whole process was entirely involuntary, 

 and that the susceptibility had arisen through the action of 

 natural selection upon favourable variations. 



