274 BUTTERFLIES 



the curious sub-family Libytlieinae of which only a 

 dozen species are now known, and these scattered 

 all over the globe. No group of butterflies exists 

 with so many anomalies of structure ; none, so far 

 removed from its nearest neighbors, which is any- 

 where nearly so poverty-stricken in forms. It is a 

 clear case of a waning type ; and that out of the 

 paltry dozen or two of fossil butterflies two should 

 be found to belong to a group wdiich cannot num- 

 ber one tenth of one per cent, of living forms is 

 indeed a surprise. It has a further interest, for 

 the existing Old World forms of this group and 

 those of the New are separated by characters which 

 ai^e unmistakably combined in these fossils, though 

 on the whole their relations are closer with the Old 

 World than the living New World type, and spe- 

 cially with a form from West Africa. The group 

 as a whole is distinctly tropical and sub-tropical 

 and widespread, so that the sub-tropical aspect of 

 the previously mentioned Florissant forms is not 

 disturbed. The food of the caterpillar, as far as 

 known, is exclusively Celtis, and it is therefore 

 interesting to note that Lesquereux has found 

 among the fossil plants of Florissant, in the same 

 beds with these fossils, two perfectly well pre- 

 served leaves of a very fuie Celtis, whose generic 



