378 Distribution of Moths of the Sub-family Bistonine. 
should (like other animals and plants of similar proclivities, 
which have migrated or advanced from Siberia)* have left 
stranded colonies in those mountainous districts, and, in the 
case of the more primitive non-Alpine WN. zonaria, similar 
colonies should be found amongst the Tertiary relicts + of 
the Altai Mountains of Turkestan, but no such colonies ,are 
known. What presses the illustration home is the significant 
absence of the Alpine forms from the Carpathians and the 
total lack of these or other species of the genus from the whole 
of Asia. 
Thus we are driven along converging paths, which must 
be followed, to the opinion that the genus is of Northern 
origin, for it is there, and there only, that the desired contacc 
with its nearest allies on all sides can be gained. 
The central or parent species of the group being far from 
mountain or northern in its predilections would, very probably, 
soon after its origin, overflow into all parts of available Europe, 
both west and east, its access to South Russia and Asia being 
barred by the western extension of the Caspian Sea to the 
Sea of Azov, and up the Volga and Don valleys, in addition 
to the enormous development of the Aralo-Caspian Basin to 
the northward in Asia. 
Therefore, in later Pliocene and Pleistocene times, when 
climatic conditions changed for the worse, N. zonaria occupied 
a fan-shaped stretch of country with its angles situated near 
Spitzbergen, the most westerly point of Britain, and in Asia 
Minor, but not extending to the southward on the west. From 
this area it had, perforce, to retreat. But when the Ice Age 
moved to its climax, local glaciers from the Alps, advancing 
to meet those from the Mountains of Scandinavia, severed 
the species into two sections, one of which massed itself in 
the Balkan Peninsula and Asia Minor which then, and for 
a long time afterwards, was continuous with Greece, Macedonia 
and Turkey ; the other just as regularly contracted its area 
toward the West. Let us consider the latter portion first. 
Sooner or later, glacial conditions supervened in the British 
area and the mountains there, together with the Scandinavian 
chain, gave birth to a system of glaciers, which, except in 
favoured nooks, ruthlessly destroyed much of. the life of 
Western Europe, both of Britain of the present day, and that 
over which the North Sea now rolls. 
Here, however, a very critical point is manifested, and 

* Like the Edelweiss (Leontopodium alpinum) the Chamois (Rupicapra 
tvagus) and the Apollo Butterfly (Parnassius apollo) to choose as illustra- - 
tions familiar Alpine forms known te everyone. 
+ As illustrated by Microbiston turanicus and M. lanavius among 
insects, and by the Walnut (Juglans vegia), Trigonotes olgae and Moricandia 
tubevosa among plants. 
Naturalist, 
