6026 



Insects, 



because Ireland has more than twice as many of them as Scotland * 

 It is believed this will be still farther confirmed by a comparison 

 drawn between Great Britain and any central portion of the European 

 Continent. 



The readers of Forbes's Essay will iind, in the relative numbers of 

 Highland and Lowland species, nothing but what agrees with the 

 hypothesis that our alpine Fauna is the more ancient, and has 

 descended to us from a period when the summits of our mountains 

 existed as islands, or m.embers of a chain of islands, communicating 

 with Scandinavia across the " Glacial Sea." In such a case we 

 should expect to find the alpine species few in number, since their 

 area was restricted from the first and its climate boreal : the insects, 

 too, may have been less able than contemporary plants to survive the 

 changes of temperature and the accidents of geological disturbances. 

 On the other hand, the higher numbers of the " British," " English " 

 and " Germanic " Types point to a more recent derivation from the 

 adjoining Continent. 



The disproportion, however, among butterflies, between the " At- 

 lantic " and " Germanic " Types, is worthy of attention, in so far as 

 these two nearly agree with Forbes's " Norman " and " North-French " 

 Floras, both of which he supposed (with some reservations) to be 

 still older than the Scandinavian " or " Highland." Now the high 

 numbers of the " Germanic " Type, the difficulty of separating it 

 satisfactorily from the " English," together with the fact of its plants 

 being found (some of them abundantly) in the centre of Germany, 

 lead to the conclusion that it is but a branch of and contemporaneous 

 with the central European, Forbes's " Great Germanic " Flora. 



Looking, on the contrary, at the " Atlantic " Type, with its fewness 

 of insect species, at the more clearly southern character of its Flora 

 (which in great measure consists of plants found towards the Atlantic 

 and Mediterranean coasts, and absent from Germany), and at its being 



* The Irish species are thirty-six : — 



British Type 20 



English Type 14 



Scottish Type 1 



Highland Type 1 



The Scotch species are thirty-three: — 



British Type 23 



English Type 6 



Scottish Type 3 



Highland Type 1 



Not one is found in either Scotland or Ireland that does not also occur in England. 

 That Ireland, with fewer plants than Scotland, should have more butterflies, shows 

 that the number of the latter is less influenced by western position than might have 

 been expected. 



