14 INTRODUCTION. 



sometimes, too, are they preserved in such a wonderful manner that in tiny 

 creatures with a spread of wings scarcely more than a couple of millimeters 

 one may count under the microscope the hairs fringing the wings. 



In attempting thus to restore the past world of our insects, two or 

 three general features have been forced upon my attention, which may 

 well be mentioned here. One of them is the remarkable fact that in hardly 

 a single instance has the same species been found at, two distinct localities. 

 These localities, it is true, are in some instances separated by hundreds or 

 even thousands of miles, and analogy with the present distribution of 

 insects would lead us to expect more or less profound changes in passing 

 from one to another. But at other times the distance is not great, or at any 

 rate not great enough to make this a satisfactory reason. It is more proba- 

 ble that the beds in which they occur are not altogether synchronous ; and 

 we are led to believe that in the separation of horizons insects will give more 

 precise and definite distinctions than may be gained by the study of the 

 plant remains of the same beds. The data at our disposal are not yet suffi- 

 ciently varied to enable us to speak with any confidence, but when the 

 other groups of Florissant insects, not considered in the present volume, 

 are worked out, and the new material that is at hand from the other princi- 

 pal localities has been fairly studied, it may be found that we are armed 

 with a new weapon of attack in solving the immediate succession of the 

 Tertiary series of the West in their finer subdivisions. 



Another point to which attention maybe drawn is the very considerable 

 number and quite extraordinary proportion of species which so far are repre- 

 sented by a single specimen. Leaving out of consideration certain marvel- 

 ously prevalent forms in the beds of Florissant, such as certain Formicidse, 

 Alydina, etc., one working these beds, from which many thousands of insects 

 have already been taken, may confidently expect that every third or fourth 

 specimen will prove something new. A quite similar statement can be 

 made of all, or all but one, of the other localities where insects have been 

 found in our Tertiary deposits : it surely indicates that with all the rich 

 results of the explorations so far undertaken we are only upon the threshold 

 of our possible knowledge. We find a richness of fauna far exceeding any- 

 thing before supposed possible. 



The interest of the Tertiary fauna is further enhanced by the discovery 

 that no inconsiderable proportion of the species in this fauna must be re- 



