RHO PALO CERA MHOMCA . 



The fauna is decidedly Palasarctic, but we have a good many wanderers from the Oriental region. 

 We have in Japan an admixture of tropical, temperate, and arctic species meeting together in the same 

 area, many of which still continue to find their way here by different routes, this being doubtless the 

 cause of another peculiarity in the Japanese fauna, to which I have called attention under the heading of 

 " dual " or twin species. That communication is continuous, is evident from the fact that we find some 

 species presenting no points of difference, while in others it is most marked ; the former are able to 

 breed true to their ancestral type, owing to frequent immigration, and those which differentiate most 

 strongly have been isolated longest. Butterflies exhibit forms in process of transmutation in greater 

 numbers than perhaps any other class of organizations, for, from their structure and wandering habits, 

 they are able to spread over large areas, and, during the space of a single year, many species pass through 

 several generations. They are thus constantly subjected, in the never-ceasing battle of life, to ever-varying 

 conditions of existence. 



I have met with some amount of opposition to my views on this subject from the hands of closet 

 naturalists, who are accustomed to " museum series " only, the dispute between the field observer and 

 the book-making describer being, even yet, very keen. 



So many new systems of classification having been proposed of late years, I think I need not apolo- 

 gize for using in this book an old one, which, notwithstanding many defects, is at any rate the most con- 

 venient for my purpose. 



My specimens have all been named by Messrs. Butler and O. Janson, and 1 am therefore not 

 accountable for any errors in nomenclature, but at the same time I must call attention to the fact that 

 many specimens named as distinct by Mr. Butler have afterwards proved to be forms of long known 

 species, and, where I have been able to detect these errors, I have included them in the list of synonyms. 



The following Families are represented in Japan : 



Papilionidae it species. 



Pieridae 12 ,, 



Lycaenidse 36 ,, 



Lemoniidae i ,, 



Nymphalidae 38 ,, 



Danaidae i )( 



Saty ridse 1 8 ,, 



Hesperidae 20 ,, 



