THE AQUATIC COLEOPTERA OF THE NORTH EBUDES 151 



upon, the absence of fish being associated with the fact that 

 no stream flowed out of the loch. 



The habitat in Mull l is a deep lochan with bottom of 

 loose stones, broken pieces of lava, and almost no vegetation, 

 the edges rapidly falling away into deep water. Buchanan 

 White compares the Mull and Strathglass habitats, the 

 latter being a loch on Ben Chearan [Beinn Acharain ?], as 

 follows : " In both localities the lochs in which the beetle is 

 found are somewhat similar in character. In both cases 

 they are near the tops of hills, in one case about 2000 ft., 

 and in the other 600 to 700 2 ft. above sea-level. In both, 

 the bottom is stony with little or no vegetation, and into or 

 out of neither of them flows any conspicuous stream. Con- 

 sequently, perhaps, no fish inhabit them. In the Strathglass 

 loch the Dytiscus occurred to me only in one corner where, 

 upon the only muddy part of the loch, rested some large 

 stones. On and under these stones the beetles rested, 

 betaking themselves to deeper water when disturbed, and as 

 they seemed very easily alarmed, repeated visits to the loch 

 resulted in only about a dozen captures." He also mentions 

 that in Mull he found the easiest way to take the beetles was 

 to turn over the stones gently, and lift the beetles with the 

 fingers as they swam slowly away. 



In my experience, gained in Norway, Skye, and Eigg, I 

 found that where D. lapponicus occurred there were no out- 

 flowing streams, and fish were apparently absent. In all 

 cases the habitats were mere lochans. 



I first took the species some years ago in Norway near 

 Fefor (Gudbrandsdal) at about 3000 ft. elevation in a small 

 deep peaty loch. In one corner of this loch was a mass of 

 vegetation (sphagnum, etc.), and here I took three specimens, 

 2 and i 9 , and a large number of nearly full-grown larvae. 

 The time of year was July. The whole bottom of the loch 

 was peat with an occasional large stone or two, but the 

 water was too deep, even at the edge, to examine these or 

 turn them over. With the Dytiscus were such British species 

 as Hydroporus wnbrosiis, palustris, and erythrocephalns, 



1 The "crater "loch above Tobermory is the habitat to which, I believe, 

 most authors refer. Alex. Somerville, however, took the species in the south 

 of the island. 



- The "crater" loch in Mull is about 775 ft. above sea-level. 



