( xli ) 



In this paper it was stated that the results of many experi- 

 ments made on Seleniu illustraria and Ennomos cmtuinnaria 

 tended to prove that both the markings and colouring 

 of the moths were materially affected by the temperature to 

 which the pupse were exposed: the markings by long con- 

 tinued exposure before the last active changes ; the colouring, 

 chiefly by exposure during these last changes, but before the 

 colouring of the perfect insect began to be visible, a mode- 

 rately low temperature during this period causing darkness, 

 a high one producing the opposite effect, and two or three 

 days at the right time appearing in some cases sufficient. 

 Dryness or moisture applied during the whole pupal period 

 had little or no effect on either markings or colouring. 

 Applying the facts thus ascertained, Mr. Merrifield said he 

 had obtained from summer pupfe of illustraria, besides moths 

 with summer markings and colouring, some moths with 

 summer colouring and spring markings, some with spring 

 markings and almost spring colouring, and some with 

 summer markings, but an approach to spring colouring. 

 These specimens, with enlarged and coloured photognxphs of 

 them were exhibited. 



Lord Walsingham thanked Mr. Merrifield for his valuable 

 paper, and said he thought that it was proved conclusively 

 that the effect of retardation by the means applied in the 

 pupal stage was to cause a tendency to the darker colouring 

 characteristic of the winter brood. If it could be established 

 that changes of temperature were a direct cause of variation, 

 not only throughout a series of generations, but in each in- 

 dividual case, the discovery would be extremely interesting, 

 especially if the insects themselves derived any distinct ad- 

 vantage from such varietal changes. 



Mr. C. Fenn exhibited a long series of E. autiwmaria, em- 

 bracing, he thought,- all the shades of colouring obtained by 

 Mr. Merrifield, though the pupte had all been kept at the 

 same temperature, in a room facing the east ; they were the 

 produce of three consecutive years, in each of which the 

 moths had been several weeks in emerging. 



Mr. Waterhouse pointed out that the temperature might 



PKOC. ENT. SOC. LOND., V., 1890. H 



