238 



CHAPTER III 



FIG. 30. Distribution of Anarta (Sympistis) 

 lapponica Thunb., a "Westarctic" moth. The 

 figured specimen is from Scandinavia. 



(Photo P. Ardo.) 



from a western direction across the North Atlantic and it is usually thought that the 

 dispersal was facilitated by one or two now submerged land-bridges. This hypo- 

 thesis was strongly opposed by Hulten (1937, e.g. pp. 126-127, 137; 1950, p. 52). 



The reasons why a Westarctic species is not always an Amphiatlantic species, 

 and vice versa, is that the former may occur in Pacific North America and northeast- 

 ern Asia (E. of River Lena) but not in the mountains of Central Europe; further- 

 more it is supposed to show clear cold-adaption. However, the essentials of the two 

 groups, above all the historical interpretation, are common to both. So it would 

 seem more appropriate to deal with them in the future under one heading. If so, 

 the term "Amphiatlantic" is much to be preferred because it is universally under- 

 stood. It would be easy to make subdivisions: into more or less pronounced Amphi- 



