i6 THE SCOTTISH NATURALIST 



only the island of Lewis. In their lists ten species of 

 water-beetles are included : — 



Hydroponis morio, Dej. 



„ obscurus, Sturm. 



Agabus bipustulatics, L. 

 llybiiis asnescens, Thorns. 

 Rhantus bistrialns, Berg. 



Dytiscus niarginalisy L. 

 Acilius sulcaius, L. 

 Gyrimts minutus, F". 



,, natatory Scop. 



,, opacus, Sahib. 



I found all these species with the exception of the first, and 

 I certainly expected to find it ! Also, I expected to find it 

 and other " mountain " species at lower altitudes in Lewis 

 than in the more southern islands, such as Eigg and Mull, since 

 these mountain species are northern in their range, and are 

 only confined to mountains in their more southern limits. 

 But neither at low levels nor at high could I find H. morio. 

 The species was decidedly scarce both in Eigg and Skye, 

 where it occurred in 6 per cent, and 12 per cent, respectively 

 of the collections, and in those cases I accounted for this 

 on the assumption that the elevation above sea-level was 

 insufficient for it to be able to oust Hydroporns gyllenJialii., 

 Schiod., which I regarded as a species complementary to it.^ 



It is difficult to believe that after making more than 

 100 collections in the island I can have missed the species, 

 if it really occurs there. I have taken it freely in various 

 parts of Scotland in June and July, so that there is no reason 

 to believe that it was merely absent in the imago state 

 during my visit, and I regard its absence as very interesting, 

 and shall refer to it again when I come to discuss the 

 question of the origin of the fauna. 



Altogether 130 collections were miade of which records 

 of the water-beetles were kept, but a number of other 

 samples were taken which were not recorded. Seventy-three 

 collections were made in the northern part, and the remaining 

 57 in the Tarbert district, and a total of 52 species resulted. 

 Forty-eight species occurred in the north, and 39 in the 

 south; 4 species were found at Tarbert which did not occur 



1 Vide " The Aquatic Coleoptera of the North Ebudes," Annals of 

 Scot. Nat. Hist.., July and October 191 1, p. 153 ; and with regard to Skye, 

 all my collecting" was done in the Broadford district, and nowhere 

 above 800 to 900 ft. 



