10 Annals Entomological Society of America [Wo\. X, 



are also other Eocene localities, such as that near Rifle, Col- 

 orado; and quite recently a small series of Coleopterous elytra 

 has been obtained in Colorado in beds which are probably quite 

 near the base of the Tertiary. The value and importance of 

 these older Tertiary insects has never been appreciated ; Scudder, 

 who described nearly all of them, was not aware of their relative 

 antiquit}^ In his work on the Tertiary weevils Scudder brings 

 out very clearly the radical difference between the Florissant 

 Fauna and what he calls the Gosiute Fauna, although "the 

 deposits of both (Florissant and the Gosiute Lake) are pre- 

 sumably of Oligocene age." When we consider that according 

 to the best information we now possess Florissant is Miocene 

 and the Gosiute Lake Eocene, all surprise at the absence of 

 species common to both vanishes. 



The Rocky Mountain Eocene insects present a rather 

 remarkable assemblage, not so much on account of what is 

 present, as for the absence of important groups. Coleoptera, 

 Diptera and Hemiptera are numerous, but prevailingly small. 

 There are a few Orthoptera and some good Odonata. A few 

 very poorly preserved ants were described by Scudder, together 

 with some parasitic Hymenoptera and a good sawfly; but 

 no bees have ever been obtained, and there is only a single 

 fossorial wasp. No Lepidoptera have yet been seen. Perhaps 

 the most interesting Dipteron is an Oestrid, represented by 

 numerous larvae.* Various families of the higher Diptera 

 were represented by genera which still exist. It is possible 

 that the conditions of deposition partly explain the character 

 of this Eocene fauna, or series of faunulae, and it is reasonable 

 to expect that further collecting will greatly modify the statistics. 

 At the same time we are lead to ask whether the complete 

 modernization of Tertiary insect life had taken place at this 

 early date; or rather, granting that the fauna so far as it goes 

 is quite modern in aspect, whether the exuberance of types so 

 characteristic of later times had yet developed. The condition 

 of affairs may, in short, have been analogous to that observed 

 in the Mammalia, which had by this time established the 

 modern outlines, but had much development and diversification 



* Dr. J. Bequaert calls my attention to the resemblance between these larvas 

 and those of the African genus Dermatoestrus. The imago of Dermatoestrus is 

 unknown. 



