( xii) 
this family the classification is not sufficiently certain to 
enable us to analyse the generic distribution, though Watson’s 
‘Revision of the Hesperiida,’* based on a somewhat hasty 
study of the species in the British Museum, shows that the 
majority of the American genera, and some of the subfamilies, 
are confined to the Neotropical region. 
Among the Heterocera the Neotropical element appears to 
be greater than among the Rhopalocera; but here again we 
have not sufficient knowledge. Packard, in his Monograph of 
the Geometrid Moths of the United States,+ gives a good 
account of their distribution (pp. 567, et seq.), with lists of the 
species inhabiting the east and west of the United States of 
America; but he does not compare these lists with those of 
Europe, and the European genera he mentions as not found 
in the United States, are probably subject to much modifi- 
cation at the present time. 
He states, however, two facts, which I can abundantly con- 
firm from my personal knowledge of the Western butterflies, 
namely, the absence on the Pacific slope of forms character- 
istic of Japan and China, and the presence there of some 
European types which do not occur in the Atlantic States. 
One of the most remarkable facts about the plant distri- 
bution of North America is that which has been abun- 
dantly proved both by the late Dr. Asa Gray and Sir J. D. 
Hooker, namely, the resemblance between the flora of the 
Eastern States and that of North-east Asia, whilst almost 
every characteristic form in the vegetation of the Atlantic 
States is wanting in California. There is, however, as far as 
I know, but little trace of a corresponding Japanese or 
Chinese element amongst the Lepidoptera, except the 
following :— 
Midea, Herr-Schaeff, a section of the genus Anthocharis, 
comprising four known species, of which one occurs in the 
Alleghany States, one in California, and two in China and 
Japan ; and Achalarus, of Scudder, of which two species, as 
recognized by him, are found in the Southern States east 
* P. Z. 8., 1898, pp. 3, et seq. 
+ U.S. Geological Survey, Vol. X., 1876. 
