On the Seasonal Dimorphism of Butterflies. 7 1 



planation to be correct, it will not apply to the 

 absence of seasonal dimorphism in cases like that 

 olPararga sEgeria and Meione, in which only one 

 isummer generation appears, so that a preponde- 

 rating inheritance of summer characters cannot be 

 admitted. Another explanation must thus be 

 sought, and I believe that I have found it in the 

 circumstance that the butterflies named do not 

 hibernate as pupae but as caterpillars, so that the 

 cold of winter does not directly influence those 

 processes of development by which the perfect 

 insect is formed in the chrysalis. It is precisely 

 on this point that the origin of those differences 

 of .colour which we designate as the seasonal 

 dimorphism of butterflies appears to depend. 

 Previous experiments give great probability to this 

 statement. From these we know that the eggs, 

 caterpillars, and pupae of all the seasonally dimor- 

 phic species experimented with are perfectly 

 similar in the summer and winter generations, the 

 imago stage only showing any difference. We 

 know further from these experiments, that tem- 

 perature-influences which affect the caterpillars 

 never entail a change in the butterflies ; and 

 finally, that the artificial production of the re- 

 version of the summer to the winter form can 

 only be brought about by operating on the pupae. 

 Since many monogoneutic species now hiber- 

 nate in the caterpillar stage (e. g. Satyrus Proser- 

 pina, and Hermione, Epinephele Eudora, Jurtina, 



