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 Leplalis ) 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 PapiHones which is ef a black colour 
with red spots ; those of Europe, on the contrary, 
present certain relations to Pamassius , 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 
