AQUATIC COLEOPTERA OF THE OUTER HEBRIDES 17 



in the north, while 13 species occurred in the north which 

 did not turn up at Tarbert. 



Species only found in the South. 



Haliplns full 'US. 

 Hydroporus incognitus. 



,, planus. 



Gyi'inus opacus. 



Species only found in the North. 



Haliplus confinis. 

 ,, ruficollis. 

 ,, laehiickei. 

 Deronectes \Z-pmtulatus. 

 Hydroporus vielanarius (i). 

 ,, memnonius. 



,, disc ret us. 



„ oh sole Ins (i). 



A gab us paludosus. 

 ,, iiebulosus. 

 ,, chalconolus. 

 Laccobius minutiis. 

 Octhebius bicolon. 



This localisation is, however, in most cases easily accounted 

 for. In the first place, some of the species were rare, only 

 a few individuals being taken (e.g., H. vielmiarius, obsolctus, 

 and mcogniti/s, H. fulvus) ; and in the second place, no 

 suitable habitat was found in the south for several of the 

 species which occurred in the north. For instance, such a 

 species as H. confinis is, in the north and west of Britain, 

 definitely a loch species, and is usually found in large lochs, 

 and on a sandy bottom, and, so far as I know, only at low 

 elevations. It was abundant in Loch Barvas More — a large 

 shallow, sandy-bottomed loch only a iQ.sN feet above sea-level, 

 and separated from the sea by a storm beach, where the 

 only other loch species was H. ivehnckei. H. confinis other- 

 wise only occurred in a sandy pool on the ground close to 

 Loch Barvas which is obviously flooded by the loch from 

 time to time. I found no suitable loch for either of these 

 species in the Tarbert district. Similarly, in the south 

 I examined no ground where I should have expected to 

 find D. i2-pustnlalus, H. vieninonius or discretus, A. paludosus 

 or nebulosus, so that there is nothing extraordinary about 

 the absence of these species from the Tarbert list. H. planus 

 occurred near Tarbert only in rock-pools above high-tide 

 mark, where the water was usually foul and possibly brackish, 

 under conditions similar to those in which it occurred in 



