THE AQUATIC COLEOPTERA OF THE NORTH EBUDES 153 



griseo-striatus is common, which are of the typical form of the 

 species. 



This lochan was the only one which I visited in Skye in 

 which the Dytiscus occurred, and it was the only one I 

 found which satisfied the conditions of having no visible 

 outflow and a reasonable depth. Quite close to it is another 

 small loch named on the ordnance map "Loch-an-Starsaich." 

 This loch is stony and comparatively shallow for some 

 distance from the edges, and has a stream running from it 

 down to Loch Eilort. Its fauna was as follows : 



Deronectes assimilis. Dytiscus punctulatus (i J ). 



Hydroporus palustris. Acilius sulcatus. 



H. erythrocephalus. Gyrinus natator. 



Agabus arcticus. G. opacus. 

 Rhantus exoletus. 



I am inclined to think, although I am speaking on 

 somewhat meagre experience, that D. assimilis and griseo- 

 striatus are what might be called " complementary " species, 

 the former occurring in lochs not highland enough for the 

 latter and the one tending to replace the other. The same 

 relationship exists, I think, in the case of Hydroporns morio 

 and gyllenhalii, the former being found in peaty pools up 

 to a certain level, above which the latter replaces it. Of 

 course no sharp line can be drawn in either case, and the 

 species overlap, but this does not invalidate the statement. 



In Eigg I found D. lapponicus in two different parts of 

 the island, and I feel certain that it occurs in one or two 

 lochans other than those in which I found it. 



Near Beinn Tighe is a series of three deep peaty lochans 

 about 850 feet above the sea. Along the sides are patches 

 of Sphagnum, Scirpus fluitans, and other water plants, and in 

 one or two places are more extensive swampy Sphagnum 

 patches which at some previous period have been open 

 water. In the water are patches of Menyanthes, of Lobelia 

 Dortmanna, and Sparganium minimum? or natans? and on 

 the bottom in the deep water Isoetes is to be seen. The 

 three lochans differ slightly from one another in their level, 

 in their flora, and in the extent of open water. Their 

 depth, especially in the case of two of them, and the 



