1891.] Mr Bateson, On Variations in colour of cocoons. 251 



The specimen measured h\ centimetres in length. The ventral 

 surface was of the usual light colour. The ground colour of the 

 dorsal surface was dark green, with a sufficient number of yellow 

 papilla? to give a yellow tinge to the specimen. There was a light 

 yellow band, from which the green was almost entirely absent, just 

 dorsal to the insertion of the legs. 



The specimen was a female, and the last leg was without a 

 white papilla. 



The genital opening was subterminal, and behind the legs of 

 the last pair. 



The uterus was full of embryos, at a stage of development 

 more advanced than in a Cape specimen killed at the same time of 

 year. 



The number of legs of the embryos was, as in the adult, 22 

 pairs. 



The specimen is of interest, as being the first recorded from 

 Natal. 



(2) On Variations in the Colour of Cocoons (Saturnia carpini 

 and Eriogaster lanestris), with reference to recent theories of Pro- 

 tective Coloration. By W. Bateson, M.A., St. John's College, 



[Abstract; received November 11, 1891. Reprinted from the Cambridge 

 University Reporter, November 24, 1891.] 



The cocoons of several moths, e.g. the Emperor and Small 

 Egger, vary in colour from dark brown to white. It is believed by 

 some that these colours have a protective value as a means of con- 

 cealment, and it has been stated by Poulton and others that when 

 spun on leaves which will turn brown, or in dark suiTOundings, the 

 cocoons are dark, while they are white if spun on white paper. To 

 account for this phenomenon " the existence of a complex nervous 

 circle" has been assumed. The present experiments shewed that 

 it is true that larvas left to spin on their food-leaves produce dark 

 cocoons, and also that if they are taken out and put in white paper 

 the cocoons are white. But it was found that larva? similarly 

 taken out and made to spin in dark substances also spun white 

 cocoons, and indeed that starvation, or merely interference at the 

 time of spinning, may lead to the production of a white cocoon. On 

 the contrary, if white paper is put amongst the food, so that the 

 larva? can, of their own choice, walk into it and spin, the cocoons 

 are generally dark. It was noticed in several cases that larva? 

 which had been shut up evacuated a quantity of dark juice having 

 the natural tint of the cocoon, and the suggestion was hazarded 

 that absence of colour in the cocoon perhaps results from the loss 

 or retention of this juice, which may be of the nature of me- 

 conium. 



20—2 



