VOL. XXI. LONDON, FEBRUARY, 1889. No. 2. 



THE LEPIDOPTEROUS FAUN.E OF EUROPE AND 

 NORTH AMERICA. 



BY A. R. GROTE, A. M., BREMEN, GERMANY. 



The Study of representative species of butterflies and moths shows 

 us that very different grades of resemblance exist between aUied forms 

 inhabiting Europe and North America. I have shown that the modifica- 

 tion shows itself sometimes mainly in the larval state ; again the perfect 

 insects depart more or less strongly. I have also ventured to decide 

 that these representative species are entitled to specific rank in our 

 nomenclature. They fulfil the condition of species, since they do not 

 intergrade, and they can be distinguished quite surely by competent 

 specialists. The study of these representative species leads to the 

 question of their relation, and we have seen that they may be regarded 

 as survivals of a former northern, circumpolar fauna, which was broken 

 up and driven southwards by the Ice Period of geologists. I have 

 originally tried to show, in Silliman's Journal, that we have in our 

 Lepidopterous fauna different elements. The representative species 

 belong to this ancient circumpolar fauna. And here belong in part the 

 identical species like Vanessa antiopa or atlanta. The identical species 

 have remained unaltered, but certain species have been introduced by 

 commerce, as the White Cabbage Butterfly and perhaps the Currant 

 Borer, Sesia tipuliforinis. The certain separation of these two sources 

 of North American species belonging to the circumpolar element requires 

 historical data which will hardly be forthcoming. The second element 

 is that which comes to us from the south, a return wave of the migration 

 southwards, which set in on the advent of the Glacial Age. This 

 southern element is divisible into such forms as have already firm foot- 

 hold, and such as the physical phenomena of the Gulf Stream, the 

 prevailing air currents during the summer, land as wind-visitors upon our 

 shores. Erebus, Aletia, Euthisanotia, among the moths, are more or less 



