278 



CHAPTER III 



per cent S E refuge 



ICELAND 

 S refuge Hot springs 



GREENLAND 



Other places 



Specimens 



DiAGR. 8. Bembidion grapei Gyll. Distribution of four types of hind-wings (a-d, 

 fig. 44) among four types of habitats in Iceland and in Greenland. 

 White = full-winged; black = strongest wing-reduction. 



In accordance with the current interpretation of the distribution of wing- 

 dimorphic forms, the most likely explanation is that the surroundings of hot springs 

 are inhabited by old populations. The index in favour of brachypterous forms is 

 almost the same as for the two large refuge areas in southern Iceland. To my mind, 

 this argues in favour of an assumption that, locally, small populations of terricolous 

 animals were able to survive the last glaciation also in other parts of the island in 

 the immediate neighbourhood of hot springs. For one of these localities, Krisuvik 

 in the Southwest, where Bembidion grapei (25 specimens) shows an index of 0.5, the 

 assumption of a glacial "micro-refugium" is confirmed by the isolated occurrence 

 of the Staphylinid beetle Othius melanocephalus Or., one of the most undoubted 

 "survivors" of the Icelandic fauna (Lindroth, 193 1, p. 484 a.f.). 



In Greenland, Bembidion grapei occurs almost exclusively in the brachypterous 

 form (fig. 47; diagr. 8). Apparently selection has been strongly in favour of flightless 

 individuals in small, isolated populations, particularly during times when glacia- 

 tion was more total than at present. A location of refuges based on the distribution 

 of Bembidion grapei seems impossible but it should be mentioned that a large 

 series of 65 exclusively short-winged individuals from Julianehaab in the South- 

 west is from the vicinity of the most famous hot springs of Greenland. 



