THE WEAK SIDES OF NATURAL SELECTION. 79 



The isolation above mentioned has not, as might at first be sup- 

 posed, tended to produce a genesis of species peculiar to the island, 

 so far as I have been able to ascertain after a thrice repeated visit 

 to the greater number of the Icelandic fjords. Interesting local types 

 and varieties of certain of the Icelandic moths beyond all question 

 do exist, but they are either such as are also found at Rannoch or 

 elsewhere in Scotland, or where not occurring in Scotland, are at 

 all events represented by precisely the same forms in other parts of 

 Scandinavia, in Finland, for example. Whether the Flora and Fauna 

 of Iceland be compared with those of the Faroes and of Scotland on 

 the one hand, or with those of Norway, Sweden, Lapland etc., on 

 the other, Iceland in either case will be found to possess quite the 

 lowest number of species of any of the aforesaid regions. The 

 great scarcity of land birds as contrasted with aquatic ditto in 

 Iceland may serve to account for the astonishing number of 

 individuals of certain species of geometridae which are thus 

 marvellously aided in their struggle for existence. The vast quan- 

 t.ties of offal and refuse of fish that lie scattered on the shores of 

 every fjord beyond all doubt tend to the perpetuation in portentous 

 numbers of such sjDecies of Diptera as habitually derive their sub- 

 s stence from garbage, while the prevalence of the Arctic Tern, as 

 delighting in similar food, is referable to the same cause. On the 

 contrary, how are we to account for the fact that Ichneumonidas are 

 very few and far between, except by the circumstance that Diurnal 

 Lepidoptera being wholly wanting, there are no chrysalids there 

 ior them to deposit their eggs in, as with ourselves ¥ Or again, 

 why is there only one species of humble bee in the whole of Iceland, 

 and why is that so rare (for I believe I was the first to report it at 

 all from the N. and E. sides of the island) except that some of the 

 flowers in which the insect delights, as the blossom of the lime, are 

 incapable of being cultivated in Iceland, and no pains whatever has 

 been taken to plant others, as the broad bean and the clover, which 

 last plant shows a straggling blossom here and there of both red 

 and white varieties, soiely from its seed having been accidentally 

 introduced along with grass seed from another land. Here in the 

 struggle for existence the perpetuation of the particular insect and 

 plant is maintained indeed, but with difficulty, and in scanty pio- 

 portions, and very locally. The utility of bees in hybridising clover 

 is so well-known, that if a live batch were introduced into Iceland 

 just as several have ere this into New Zealand, fragrant plant and 

 winged bee might aet and react on each other beneficially were it 

 not ior the utter want of enterprise and industry displayed by the 

 Icelander. In conclusion, with regard to Diptera once more, genus 

 Eristaiis occurs in the Faroes but not in Iceland, and I was told by 

 a noted British entomologist, that if I wanted to find Eristaiis in 

 Iceland, I had only to run a drain there, but for al! that one species 

 of genus Helophilus is found in Iceland, and that genus both there 

 and at home delights fully as much in the neighbourhood of drains 



