PREFACE. 



When, in January, 1886, the Division (.f Fossil Insects of tlie V. S. 

 Gooloo-iciil Sni'vey was established, and I entered upon my duties therein, 

 I had still in liiind in an iuooniplete condition a report upon our Tertinry 

 insects for tin- T. S. Geolo<)-ical Survey of the Territories, under 1 )r. F. V. 

 Hayden, the i)lates for which were already finished. Tliis work, which 

 was completed early in 1890, contained a ftdl account of all the Tertiary 

 insects (tf our country known up to within a few years, as far as re"-arded 

 the lower orders; but the hi<,dier orders, and especially the Coleoptera, 

 Diptera, and Hymeuoptera, which comprised those richest in material, were 

 left nearly untouched, only the earliei- found specimens in the Green river 

 beds, and which had already been engraved on the plates, being- included, 

 lea^^ng the far richer fauna of Florissant, Colorado, entirely untouched. 



The elaboration of this immense amount of material, enlarged by 

 additions from other localities, including some new and i-ich, was begun 

 immediately upon the completion of the Hayden reixirt, and the ja-esent 

 work is a iir.st instalment toward a hi.story of our tassil Coleoptera. In 

 the diAasion treated are included 193 species, all Imt one of which come from 

 the older Tertiaries, while there have been described (or merely indicated) 

 from the European Tertiary rocks onl}- loO species, of which !» come from 

 the Pleistocene. Our older Tertiary rocks, therefore, are found to have 

 already yielded nearly 28 per cent more forms than the corresiionding 

 European beds. It is altogether probable, such is the extent and richness 

 of the fresh-water Tertiary deposits of the West, that this ijrojjortion will 

 be largely increased in the future, particidarly as the exploitation of our 

 Tertiary insect deposits has been merely begun; the number of persons 

 who have been engaged in any field-work upon them ma\- lie counted 

 up<pn oiu-'s fingers, and no natimilist besides myself has yet undertaken 

 their study. 



S. II. S. 



