Distribution of Moths of the Sub-family Bistonince . 317 



settlers but, from its geographical limitations, its small exten- 

 sion in a north and south direction, all it could receive was 

 a quota of temperate forms from Asia and a small proportion 

 of other forms (which, since they have now deserted us, need 

 not be considered) reinforcing its Glacial survivors. The 

 bulk, if not all, of species seeking to become naturalised 

 Europeans could only come from Eastern Asia, and thus from 

 the very area whence the new temperate element in Pacific 

 America advanced. 



Wherefore, in a broad way, the dwellers in the two regions 

 must coincide, although plainly they may, as indeed they do, 

 differ in detail. 



Amongst such components of common origin, in the 

 Lepidoptera are to be found, Callophrys rubi, replaced in far 

 western America by C. dumetorum, Parnassius delius by P. 

 sminthens, Papilio machaon by P. zolicaon, Saturnia pavonia 

 by 5. mendocino and, lastly, the objects of our investigations, 

 Coniodes plumigeraria, representing the development, already 

 foreshadowed in P. (?) verecundaria, of the genus Phigalia. 

 Our insect yields us then in Pacific America a metamorphosis 

 of Phigalia, which, pressing on from Asia, crossed the Behring 

 area and, kept within bounds by the Rockies, skirted the 

 coast finally to organise all suitable ground from Alaska to 

 Southern California. 



However, the Post-pleistocene promise of warmer days 

 was not kept. Gradually, the annual isotherms favourable 

 for the continuance of the insect in its northernmost abodes, 

 slipped to the south ; with them passed the insect until it was 

 pressed within its limits of to-day in British Columbia, Cali- 

 fornia and Colorado — there to be an ever-present terror to 

 the twentieth century walnut grower. To the genus Juglans 

 it has transferred its attentions from Quercns, Ulmus, Salix 

 and the like. 



Thus we see how it happens that Phigalia occurs in a 

 typical form in the Appalachian subregion but is replaced, 

 on the other side of America, by the allied genus Coniodes. 



XIV.— THE GENUS APOCHEIMA (HUBNER). 



Apocheima hispidaria (S.V.). Distribution : — Central Eur- 

 ope, North and Central Italy, Northern Balkans, East-central 

 Siberia. 



Apocheima cineraria (Ersch.). Eastern Turkestan, Bokhara 

 and Samarkand. 



In Apocheima is to be recognised a branch from the main 

 stem of which Microbiston is the modern representative. 

 Indeed, allowing for the dwarfing of the latter genus, an 

 almost inevitable result of its desert abodes, there is but little 



1917 Oct. 1. 



