1885.] The Colouring of Phytophagous Larvoe. 269 



ceeding those which produce the maximum elongation of iron. The 

 greatest observed retraction of nickel is more than three times the 

 maximum observed elongation of iron, and the limit has not yet' been 

 reached. 



12. A nickel wire stretched by a weight undergoes retraction when 

 magnetised. 



III. " The Essential Nature of the Colouring of Phytophagous 

 Larvae (and their Pupse) ; with an Account of some 

 Experiments upon the Relation between the Colour of 

 such Larvae and that of their Food-plants." By Edward 

 B. Poulton, M.A., of Jesus and Keble Colleges, Oxford. 

 Communicated by Professor J. S. Burdon Sanderson, 

 F.R.S. Received April 11, 1885. 



CONTENTS. 



1. The essential nature of the colouring of Phytophagous larvae. 



2. Methods by which the two factors of larval colouration may be recognised : 



instances of their occurrence. 



3. The different results of methods of preservation upon the two factors in larval 



colouration. 



4 Colours due to larval tissues independently of pigment. 



5. Changes in the two factors of larval colouration before pupation. 



6. The causes of colour in pupae. 



1. The ultimate use of the derived pigments. 



8. The probable history of larval colouration. 



9. Spectroscopic examination of the blood of Lepidopterous larvae and pupae. 



10. Comparison of the above results with those yielded by unaltered plant pig- 



ments. 



11. Conditions under which the derived pigments exist in the larvae, &c. 



12. Notes upon the physiology and chemistry of the blood of larvae and pupae. 



13. The relations between the colour of Phytophagous larvae and that of their food- 



plants. 



14. Experiments upon the larvae of Sphinx Ligustri. 



15. Experiments upon the larvae of Smerinthus Ocellatus. 



16. Observations in the field upon larvae of S. Ocellatus during 1884. 



17. Experiments upon captured larvae of S. Ocellatus. 



18. The protective character of the variations in the larvae of S. Ocellatus. 



19. The complex nature of the influence of the food-plant upon the larvae of S. Ocel- 



latus. 



20. A suggested explanation of the larval tendency towards certain colours inde- 



pendently of the food-plant. 



21. The essential nature of the changes in colour produced by food-plants. 



22. Summary : and conclusion as to the nature of the influence of the food-plant. 

 Explanation of Spectrum chart. 



