222 NATURAL HISTORY BULLETIN. 



among the beetles. Good examples may be found among the 

 Meloidae, Tenebrionidae and epigaeal Rhynchophora. Occa- 

 sionally these forms leave their natural haunts and extend for 

 long distances up the river valleys. Thus Eleodes may some- 

 times be met with at altitudes exceeding ten thousand feet. 

 As we enter the timbered country on the higher foot-hills and 

 lower mountain sides, we encounter a fauna which while not 

 unmixed with species that have come up from the plains, 

 shows a strong affinity to the life about our Great Lakes. 

 Higher still — that is to say from about eight thousand to nine 

 thousand feet, according to the exposure, presence or absence 

 of near-by snow-fields and so on — we meet with many species 

 of genera still more boreal in habits. We may mention 

 Nebria with its many species, usually taken along the coldest 

 mountain streams, the flattened Bembidia, and the large 

 Aphodii. Above timber line the peaks sustain a few beetles 

 which seem to be of arctic origin, left, probably, by the 

 retreating ice-sheets of the Glacial period. 



I cannot agree with Prof. Cockerell 1 who claims that the 

 Glacial epoch would, for the time being, result in the almost 

 complete extermination of the insect fauna of Colorado and 

 the adjacent table-lands. He assumes that the arid region 

 " where not actually glaciated would be a frozen desert," 

 something which I think is not indicated by such geological 

 evidence as we possess. The glaciation of Colorado was 

 apparently not particularly extensive. Neither does it seem 

 likely that the western ice-sheet went so far south as San 

 Diego; at any rate the indications seem to show that along 

 the highlands of Southern California only the loftier mount- 

 ains were glaciated at all. Today great glaciers exist in the 

 immediate vicinity of well-wooded districts rich in animal 

 life. The same phenomenon may have occurred during 

 ancient times. 



For the present I refrain from discussing the correlation 

 between alpine and isothermal life-zones; the more readily as 

 I hope soon to treat the matter from a standpoint different 



1 Transactions of the American Entomological Society, Vol. XX, p. 319. 



