20 Proceedings of the Royal IrisJi Academy. 



Tabular Summary of Distribution. 



lu the foregoing table (pp. 18-19) an attempt is made to show the distribu- 

 tion of the species of Collembola known to inhabit Spitsbergen and Bear Island, 

 both as regards the various islands of the archipelago and generally. In a 

 few cases where no more definite locality than " Spitsbergen " is recorded for 

 a species, it is taken for granted that the insects were collected on the 

 frequented West Island. The other regions included show generally the 

 range of the Spitsbergen springtails ; and in the selection preference has 

 been given to countries the CoUembolan fauna of which is fairly well known. 



Distributional Notes. 



A glance at the tabular list of Spitsbergen Collembola shows that most of 

 the species have a wide range in the Arctic regions and in temperate Europe. 

 Ackorutes viaticus is probably well-nigh cosmopolitan. A few species are 

 seen to be exclusively or characteristically Arctic: Ackorutes Injixrloreus 

 (this form, however, has not been recognized by modern workers at the 

 group ; and it may be founded on aberrant A. viaticus), A. Tidlbergi, 

 Tetracanthella inlosa, Onychiurus arcticxis, and 0. f/roenlandicus. It will 

 be noticed that Ackorutes longisjnmcs, Archisotoma Beselsi, and Agrenia 

 bidenticulata are common to the Arctic regions, to our own islands, 

 and to Scandinavia and Finland, while apparently absent from the central 

 European lowlands ; the two former of these three insects are found also in 

 America, while the other is represented on the Swiss mountains. Such 

 distribution, showing affinity between the fauna of America and that of the 

 Arctic regions and northern and western Europe, has been noticed in many 

 groups. It supports the view that land connexions probably existed to the 

 north of the Atlantic in Tertiary and Pleistocene times; and the dis- 

 continuous range of such insects as the three mentioned above suggests for 

 them a comparatively high antiquity. This is especially true of Arckisotoma 

 Beselsi, a most distinct and apparently archaic type of its family, which 

 ranges as far south as Tierra del Fuego, and is represented by a closely allied 

 species on the South Orkneys in the Antarctic Ocean. Belief in the 

 " accidental " passage, over wide sea-channels, in high latitudes, of these 

 minute and frail insects is not easy of acceptance ; and the fact that at least 

 two species of Collembola now inhabit the Antarctic continent helps us tO' 

 consider the probability of the survival of some members of the order in the 

 Arctic regions, even through the period of severest glaciation. 



