THE CANADIAN ENTOMOLOGIST. 167 



haps, in Colorado. As on islands in the air, these insects have been 

 left by the retiring of the ice-flood during the opening of the Quarternary. 



On inferior elevations, as on Mount Katahdin, in Maine, where we 

 now find no Oeneis butterflies, these may formerly have existed, succumb- 

 ing to a climate gradually increasing in warmth from which they had no 

 escape; while the original colonization, in the several instances, must have 

 always greatly depended upon local topography. 



In conclusion, I have briefly endeavored to show, that the present 

 distribution of certain insects may have been brought about by the phe- 

 nomena attendant on the glacial epoch. The discussion of matters 

 connected with this theoretic period of the earth's history still, as it now 

 appears, brings out more and more clearly the conception of its actuality. 

 I hope that my present statements may draw the attention of our zoolo- 

 gists more to the matter, seeing that we have in our own country fields for 

 its full exploration. And I permit myself to entertain the belief that 

 testimony as to the former existence of a long and widely spread winter 

 of the years, is offered in evidence through the frail, brown, Oeneis butterflies 

 that live on the tops of the mountains. 



METHODS OF SUBDUING INSECTS INJURIOUS TO 



AGRICULTURE. 



BY JOHN L. LECONTE, M. D., PHILADELPHIA. 



(Read before the American Association for the Advancement of Science, at 



Detroit, Aug. 10th.) 



In accordance with the predictions made at the time of its first 

 appearance in the immediate Mississippi Valley, the Colorado potato 

 beetle continues to extend its area of distribution. It has during the last 

 and present seasons reached the Atlantic coast of the Middle States, and 

 is preparing an invasion in mass of the maritime parts of New England, 

 which will soon be overrun with the same ease with which it has con- 

 quered the Western and Middle States. Meanwhile the farmers are 

 anxiously inquiring for means of destroying the invader. Materials 

 destructive to the insects and said not to be injurious to the plant or the 

 soil, have been recommended almost without number ; but with the 



