APHIDES OF FLORISSANT. 159 



and certain conclusions as to their age can be made 

 from the evidence alone of the entombed insects. Mr. 

 S. H. Scudder thinks that some revision of the CEninsfen 

 and Radoboj insects must be made before a good 

 comparison can be of value between the two continents 

 as to age. 



It is remarkable that no certain traces of insects 

 have yet been noted in beds of the Pliocene period ; 

 and this paucity of insects also in the Quaternary or 

 Post-Tertiary superficial deposits is equally noticeable. 

 Possibly the nature of the deposits in these compara- 

 tively recent times were unfavorable to their preserva- 

 tion, as has been suggested by Goss and others. 



Remains of Coleoptera, chiefly elytra, have been found 

 in peat-beds, and in brick-earth in several parts of 

 Great Britain, Switzerland,* and North America ; but 

 the Hemiptera do not seem to have left their remains 

 in such a condition as will allow of their identification. 



The Glacial and Drift periods appear to have been 

 ill adapted for the preservation of insects. 



Probably the lower temperatures of the epoch just 

 before the appearance of man on the earth were 

 inimical to such. With the exception of a few beetles 

 it is believed that no fossil insects have been described. 



* Prof. Heer, < Der Urwelt,' 1865, p. 481, &c. 



