DISTRIBUTION 



323 



strongly manifest throughout the fossil series, though among recent 

 insects Sialidae occupy only a subordinate place. Strange to say, few 

 aquatic insects have been found in this ancient lake basin. 



Fossil butterflies are among the greatest rarities, only seventeen 

 being known; yet Florissant has contributed eight of these, a few of 

 which are marvelously w T ell preserved (Fig. 304), as appears from Scud- 

 der's figures. Two of the Florissant specimens belong to Libytheinae, 

 a group now scantily represented, though widely distributed over the 

 earth. The group is structurally an archaic one, and its recent members 

 (forming only one eight-hundredth of the described species of butter- 

 flies) are doubtless relicts. 



Taken as a whole, the insect facies of Tertiary times was apparently 

 much the same as at present. The Florissant fauna and flora indicate, 

 however, a former climate in Colorado 

 as warm as the present climate of 

 Georgia. 



Quaternary. The interglacial 

 clays of Toronto, Ontario, have yielded 

 fragments of the skeletons of beetles to 

 the extent of several hundred speci- 

 mens, about one third of which (chiefly 

 elytra) were sufficiently complete or 

 characteristic to be identified by Dr. 

 Scudder, who has found in all 76 species 

 of beetles, representing 8 families, 

 chiefly Carabidae and Staphylinidas. 



All these interglacial beetles are referable to recent genera, but none of 

 them to recent species, though the differences between the interglacial 

 species and their recent allies are very slight. As a whole, these species 

 ''indicate a climate closely resembling that of Ontario to-day, or perhaps 

 a slightly colder one. . . . One cannot fail, also, to notice that a 

 large number of the allies of the interglacial forms are recorded from the 

 Pacific coast." (Scudder.) The writer, who has studied these speci- 

 mens, has been impressed most by their likeness to modern species. It 

 is indeed remarkable that so little specific differentiation has occurred in 

 these beetles since the interglacial epoch certainly ten thousand and 

 possibly two or three hundred thousand years ago. 



General Conclusions. Unfortunately, the earliest fossils with 

 which we are acquainted shed much less light upon the subject of insect 

 phylogeny than one might expect. The few r Devonian forms, though 



FIG. 304. Prodryas persephone, a 

 fossil butterfly from Colorado. Natural 

 size. After SCUDDER. 



