82 INTRODUCTION. 



selves, however, that the combinations which we 

 have made are altogether free from blame, any more 

 than those of our predecessors. When occupied 

 with the productions of a single country, the classi- 

 fication is much more easy ; the greater number of 

 species associate pretty well with each other, and, 

 if we except a few of the most anomalous, a series 

 is obtained free from much irregularity. In this 

 way, the European species form a pretty homoge- 

 neous assemblage, and the same thing holds with 

 regard to those of South America, New Holland, 

 or any other country taken by itself; but when we 

 attempt to classify those of the whole globe, we fre- 

 quently meet with intermediate genera which in- 

 terrupt this harmony. If we even take a somewhat 

 numerous genus belonging at the same time to several 

 different countries, we find species which form a 

 passage to other races proper to each of these coun- 

 tries. For example, the genus Pieris of Latreille 

 offers species in America (genus LeptalisJ which 

 bear a perfect resemblance to the Heliconii in their 

 colour, the length of their bodies, and narrowness of 

 the wings. Others of the same country (genus 

 Euterpe) insensibly unite with that division of 

 American Papiliones which is of a black colour 

 with red spots; those of Europe, on the contrary, 

 present certain relations to Parnassius, Pieris Cra- 

 tcegi appearing to form the passage to P. Mnemo- 

 syne, while those of India gradually approach Colias 

 through P. Judith and P. Panda, and to Danais 

 with green spots through P. Valeria. All other 



