AQUATIC COLEOPTERA OF THE OUTER HEBRIDES 65 



List of Species — continued. 



Dytisciis punctulatus, F. 

 ,, marginalis^ L. 



Aciliiis sulcalus, L. . 



Gyrinus iniiiiilus., F. . 

 „ natator, Scop. 



„ opacns, Sahib. 

 Hydrobius fuscrpes \a.t. picicrus^ Sharp 



Philhydrus fuscipennis^ Thorns. 



Paracymus ttigroceneus, Sahib. 

 A naccena globulus, Payk. . 

 Laccobius alutaceus. Thorns. 



,, minutus, L. 



Limnehius truncatellus. Thorns 

 Helophorus aquaticus, L. . 



,, viridicollis, Steph. 



„ brevipalpis. Bedel. 



Octhebiiis bicolon, Germ. . 



22 



4 

 21 



29 



30 



2 



I 



26 



12 



28 



6 



I 



Full-grown larvoG occurred two 

 or three times. 



In the south, full-grown larvae 

 occurred commonly in one 

 large peat-hole at about 950 

 ft. Several imagines occurred 

 in one pond m the north. 



Probably much commoner than 



the figure indicates. 

 Quite common where it occurred. 

 All specimens were definitely of 



the p icier us foim. 

 = Ph. melanocephalus^ Brit. 



auct. pars. 



= lenetpenniSf Thorns. 



Abundant in pools in the sea- 

 turf behind Melbost sands. 



Of all the species of water-beetles in the foregoing list 

 very few are to be described as rarities, and the vast majority 

 of them are to be found in any part of the British Islands ; 

 for instance, only about 8 or 9 species in the list do not 

 occur in East Anglia. Almost the only types of habitat in 

 the Hebrides are lochs, peaty pools, and streams, and the 

 lochs and streams are exceedingly poor in species, so that 

 the water-beetle fauna consists almost entirely of those 

 species which can tolerate acid peaty water which, using 

 a botanical term, would be called " oxylophils," although in 

 most cases at least the insects endure rather than appreciate 

 their conditions, as is to be Inferred from the fact that they 

 are much more abundant under other circumstances. 



If we compare the list of species with those of other 

 western islands, we find that, with very slight variations, the 

 same species head each list: — 



39 



