EOCENE INSECTS FROM THE ROCKY MOUNTAINS. 



By T. D. A. COCKERELL, 



Of the University of Colorado, Boulder. 



The insect fauna of the Rocky Mountain Eocene is of peculiar 

 interest and importance. We know very little of the insects of the 

 later Mesozoic. From the Cretaceous, excluding objects regarded as 

 egg-masses, galls, etc., vre have records of nineteen species of insects, 

 of which four are North American, coming from Manitoba, Montana, 

 Colorado, and Tennessee respectively. Of the nineteen Cretaceous 

 species, no less than fourteen are Coleoptera, the others being refer- 

 able to the Homoptera (Cicadidae and Fulgoridae). Trichoptera, 

 Blattoidea, and Odonata. No doubt the modernization of insects 

 and the development of most of the existing families took place during 

 the later part of the Mesozoic, but we have so little knowledge of the 

 in ect-fauna that we can only infer what may have taken place. 

 Below the Cretaceous, we find Looustidae (sens, lat.), Gryllidae, 

 Gomphidae, Epallagidae, Mycetophilidae, Bibionidae, Psychodidae, 

 Tipulidae, Nemestrinidae, Nepidae, Belostomidae, Naucoridae, 

 Notonectidae, Corixidae, Fulgoridae, and Jassidae; that is to say, 

 families of Orthoptera, Odonata, Diptera, Heteroptera, and Homop- 

 tera which are still living. The numerous Coleoptera are also doubt- 

 less at least in part referable to existing families. Thus the Mesozoic 

 insects are very modern in appearance when compared with those of 

 the Paleozoic; but it is not until Vv^e come to the Eocene that Vv^e find 

 an extensive fauna of essentially modern type, including a number 

 of genera still living. The records of Eocene insects, outside of the 

 Rocky Mountams, are very few. Eleven, nearly all beetles, are 

 recorded from Greenland; one beetle from Grinnell Land; seven 

 species from Italy; four from England;^ 23 species altogether. An 

 odonatid larva {Austrolestidion duaringae Tillyard) from Australia 

 is perhaps Eocene, possibly Cretaceous. Thus, were it not for the 

 Rocky Mountain Eocene, we should be v/ithout a satisfactory Ter- 

 tiary insect-fauna lower than the Oligocene, the time of the Baltic 

 amber. From the Eocene rocks, generally classed as of Green River 



I Since this was written I have received and described twenty-seven additional British Eocene insects. 

 The material belongs to the British Museum. 



Proceedings U. S. National Museum, Vol. 57— No. 2313. 



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