328 HISTORY OF THE EUROPEAN FAUNA. 



the route they came by is the Oriental and not what 

 I have called the Siberian. 



Take, for instance, the genus Nebria, of which we 

 have one species in England a black insect with a 

 bright reddish-yellow border and long light legs 

 known as N. livida. There are about eighty Euro- 

 pean species, most of which are confined to the Alps, 

 the Caucasus, the Pyrenees, Spain, and Greece. The 

 genus, however, ranges all over the Holarctic Region, 

 that is to say roughly, over Europe, Central and 

 Northern Asia, and North America. The centre of 

 distribution lies in Central Asia. If the genus had 

 poured into Europe by the northern or Siberian 

 route, we should probably now find many species in 

 Northern Russia, Germany, and France ; but this is 

 not the case, and we may therefore assume with some 

 justification that the Southern or Oriental route was 

 the only one available at the time when the bulk of 

 the species of Nebria wandered to Europe. Many 

 of the Nebrias occur in Switzerland and in the Alps, 

 generally on the margins of the snow-fields and 

 glaciers, like N. Germari and Brunii. Others, for 

 example, N. atrata, ascend to the highest limit of 

 animal life, having been observed at a height of over 

 10,000 feet. 



Of the remaining orders of insects we know as yet 

 very little. Central Asia and even Siberia are only 

 beginning to be explored, and their invertebrate 

 fauna except Lepidoptera and Coleoptera is practi- 

 cally unknown. However, I cannot conclude this 



