VI. 



Colour Changes in Insects. 



THE question of the variation in colour and markings exhibited by 

 many species of lepidoptera, in both their preparatory and 

 perfect stages, has, during the last few years, received much atten- 

 tion, and given rise to not a little controversy. A general protective 

 resemblance of insects to their surroundings has long been an 

 accepted fact with most naturalists, and no one would deny that the 

 special and often highly perfect likeness of caterpillars to twigs and 

 imagines to leaves, is of value as a protection ; but on the meaning 

 of the variation in colour of a species with reference to its surround- 

 ings, less certainty has existed. This most interesting subject was 

 brought into prominent and public notice in 1890, by Poulton, in his 

 well-known book, "The Colours of Animals " (pp. 1 10-158). Some 

 doubt has lately been expressed as to certain of his deductions. His 

 recent publication (i) of the details of several years' experiments, of 

 which only some of the leading results were given in " The Colours 

 of Animals," is, therefore, of value, and a short review of the questions 

 raised may be of interest. 



The only larvae of Noctuid moths on which Poulton experimented 

 were those of Hadena oleracea, Euplexia lucipara, two species of Mamestm 

 (M. brassiccB and M. persicariis), and four of Catocala (C. sponsa, C. mipta, 

 C. fraxini, and C. elocata). The Mamestm showed no power of colour- 

 adaptation, some green caterpillars of M. persicariis turning brown on 

 green leaves. Most noctuid larvae feed by night, hiding in earth by 

 day, and colour is consequently of minor importance to them. The 

 Catocala larvae, which in their form and habits approach geometers, 

 were rather sensitive to environment, tending to become darker when 

 black twigs were mixed with their food, than when among green 

 leaves and shoots only. Poulton's results with these two genera are 

 confirmed by Miss Gould (2). No certain results were obtained with 

 the larvae of Hadena and Euplexia. 



The only geometrid caterpillar which was not proved sensitive to 

 its environment was that of Ephyra anniilata {omicronaria). All others 

 on which experiments were made were darkened by placing black twigs 

 among their food. Such were the larvae of Ennomos queninaria {angnlavia), 

 Selenia lunaria, Melanippe montanata, Phigalia pedaria (pilosaria), Hemero- 

 phylla abruptayia, and Crocallis elinguaria. All these were light brown 

 among green leaves and shoots. The last-named caterpillars were 



