50 Studies in the Theory of Descent. 



believe this species to be extraordinarily indifferent 

 to climatic influence ; but the South European 

 summer generation differs to a not inconsiderable 

 extent from the winter generation just mentioned, 

 the brilliant coppery lustre being nearly covered 

 with a thick sprinkling of black scales. (Plate II., 

 Fig. 22.) The species has thus become seasonally 

 dimorphic under the influence of the warm 

 southern climate, although this is not the case in 

 Germany where it also has two generations in 

 the year. 5 No one who is acquainted only with 

 the Sardinian summer form, and not with the 

 winter form of that place, would hesitate to regard 

 the former as a climatic variety of our P. Phlczas ; 

 or, conversely, the north German form as a 

 climatic variety of the southern summer form 

 according as he accepts the one or the other as 

 the primary form of the species. 



Still more complex are the conditions in another 

 species of Lyccenidce, Plebeius Agestis ( Alexis 

 Scop,), which presents a double seasonal dimor- 

 phism. This butterfly appears in three forms ; in 

 Germany A and B alternate with each other as 

 winter and summer forms, whilst in Italy B and 

 C succeed each other as winter and summer 



* [Eng. ed. From a written communication from Dr. 

 Speyer, it appears that also in Germany there is a small dif- 

 ference between the two generations. The German summer 

 brood has likewise more black on the upper side, although 

 seldom so much as the South European summer brood.] 



