THE INFLUENCE OF THE MUTATIONS OF THE 

 PLEISTOCENE LAKES UPON THE PRESENT 

 DISTRIBUTION OF CICINUELA. 



H. F. WICKHAM. 



With the propagation of the late theories of Hfe-zones founded 

 upon temperature conditions, has come about a neglect of those 

 considerations, of a more obscure though not less important 

 nature, which we must recognize if we are to attain anything 

 more than a superficial understanding of geographical distribu- 

 tion. The zonal theory as expounded by some of its more stead- . 

 fast adherents has the apparent advantage of simplicity and 

 moreover appeals directly to the ' practical man ' since it is with- 

 out doubt correctly assumed that most of our cultivated plants 

 as well as numerous wild ones are limited to certain belts which 

 are more or less closely coincident with the isotherms. The 

 theory works well with agriculture in general, but it only 

 imperfectly expresses the truth if we apply it to the natural 

 distribution of Coleoptera on this continent. By natural, I mean 

 original, in the sense of not being modified through the agency 

 of civilized man ; for cultivation and settlement have been i)()tcnt 

 factors in changing the range of numerous species, otten 

 resulting in the rapid extermination of the most charattci istic 

 types of a district and their replacement by others. Harriers 

 which a few years ago were amply sufficient to pre\ ent the inter- 

 mingling of life of two nearby regions become no longer effective 

 and the Faunae and the Florae become contaminated l)y the 

 encroachment of strangers. Irrigation changes the nature of 

 entire counties, lakes are drained, mountains are denuded ot their 

 forests and can no longer support the life which has been theirs 

 for thousands of quiet years. 



While it has been known for many years that the geological 

 history of a given region has exercised a profound influence upon 

 the present Fauna and Flora ; while the effects of the Glacial 



