1903] WEBSTER: — DIFFUSION OF INSECTS c^ I 



point. Lina lapponica, one of the Chrysomelidae, in Europe occurs only in the far 

 north and on the highest mountain ranges, feeding, as with us, on willow ; but in 

 North America it has become diffused in the lowlands to the southwest part of the 

 country, from Alaska to Texas. A vile-odored carabid beetle, Noitiius pygfnaens, 

 occurs only rarely in southern France, Hungary, and Greece, while in North Amer- 

 ica it is found in the Appalachian mountain system from Georgia northward to 

 Nova Scotia, and in Canada, Washington, and Oregon, thus describing in its distri- 

 bution an almost complete half circle. How it ever reached this country is still a 

 mystery. These instances are cited here in order to show that it is not at all extra- 

 ordinary for insects to be found in the far north in the eastern hemisphere and in 

 the far south in the western. 



Again, insects found in high altitudes in the tropics may be closely related to 

 others occurring in the lower lands farther to the north. A good illustration of this 

 is offered by a species of Hemiptera belonging to the genus Emesa, found almost 

 directly under the equator at an elevation of 16,500 feet above sea level, — the 

 highest altitude at which animal life has ever been found, — but whose nearest ally 

 is Efnesa longipes, a bug that is common all over the middle west, and at elevations 

 of not over five or six hundred feet, 



Diffusion from the Southwest. 



{See map. A, Pacific Maritime: B, Tropica/ Stibalpine: C, Atlantic Maritime.) 



We will now pass to a consideration of diffusions from the southwest. Central 

 America and Mexico have long seemed to me to be biological headquarters, veri- 

 table insect nurseries for the propagation of new species to be sent northward. It 

 is here that we have the greatest wealth of material and, I regret to add, the least 

 knowledge thereof, for these countries are far more healthy for insects than for 

 entomologists. I never see a collection of insects from that country, or read of 

 those that are known to occur there, that I do not devoutly hope that some institu- 

 tion with funds to be devoted to research may have this lack of information 

 brought to its notice. 



In discussing the northward diffusion of South and Central American forms, I 

 shall be obliged to select two or three genera as typical, and with but an occasional 

 exception confine myself to them, though others might be chosen as illustrations 

 nearly or quite as satisfactorily. 



The old genus Halisidota, among the moths, and Diabrotica and Myo- 

 CHROUS, of the Coleoptera, though perhaps no better illustrations than others, are 

 such as I am best acquainted with, having given them somewhat careful study. 



