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XII. On Variation in the Colour of Cocoons, Pvpcs, ami 

 LarrcB : farther experiments. By William Bateson, 

 M.A., Fellow of St. John's College, Cambridge. 

 Communicated by Dr. David Sharp, M,A., F.R.S. 



[Read October 5th, 1892.] 



I. The colour of the cocoons of Saturnia carpini. 



In the Trans. Ent. Soc. Lond., ]892, Part I., p. 45, 

 I gave an account of some experiments touching the 

 variation of the colour of the cocoons of the Small 

 Egger (Eriofiaster lanestris), and of the Emperor Moth 

 {Saturnia carpini). It has been stated by Poulton* and 

 others that the familiar variation of these cocoons, from 

 coffee-brown to a cream -white colour, takes place in 

 accordance with the substances to which the cocoons 

 are attached, and the inference was suggested that this 

 variation in colour was a protective adaptation to render 

 the cocoons inconspicuous. The evidence which I 

 l)rought forward went to show that the statement that 

 there is any relation between the colour of these cocoons 

 and that of the substances, to which they are attached, 

 was founded on a mistake. In the case of Eriogaster, 

 experiment showed 



(1) That caterpillars left to spin in the leaves of 

 the food-plant (hawthorn) spin dark cocoons. 



(2) That caterpillars taken away from their food 

 and shut up spin liglit cocoons, whether the sur- 

 roundings in which they are confined are black 

 or white. 



(3) That caterpillars which of their own choice 

 crawl into and spin in white paper placed amongst 

 their leaves spin dark cocoons. 



From these results it was to be concluded that the 

 cause determining the production of light cocoons was 

 removal from the food, or the state of annoyance in- 

 cident to such removal, and that in fact the light- 



* E. B, Poulton, 'Colours of Animals,' pp. 142 — 146. 

 TRANS. ENT. SOC. LOND. 1892. — PART III. (nOV.) 



