AQUATIC COLEOPTERA OF THE OUTER HEBRIDES 6i 



rich, as in May and June, out of forty-seven collections made, 

 ten produced more than 30 species ; but we cannot assume 

 that what is true for East Anglia is true for the Hebrides ; 

 in fact, there is every reason to believe that there is much 

 less tendency to variation in the west than in the east of the 

 Britannic area. 



One interesting aspect of the average of species per 

 collection is its relationship towards the total number of 

 species in the locality, and in the last column in the table 

 I have shown this in terms of percentage for all the places 

 mentioned. It will be seen that the figure varies from 4-9 to 

 8-5 ; that is, in one place only 4-9 per cent, of all the species 

 in the district occurred in the average collection, while in 

 another 8-5 per cent, occurred. It is noticeable that although 

 the highest percentage occurs in the western islands, and the 

 lowest in East Anglia, the figures do not diminish steadily 

 towards the south-east. As is shown by the two figures for 

 July and September, in East Norfolk there is a marked 

 difference even in the same locality in different months, and 

 perhaps the most significant point is that there is only 

 31 per cent, between the extremes. 



The only other point in the table (p. 20) which seems 

 worth attention is the proportion of Hydradephaga and 

 Hydrophilidae in the different localities. Whereas there are 

 less than three times more Hydradephaga in the average East 

 Anglian collection than in the average Lewisian, there are 

 more than four times as many Hydrophilidae, the latter 

 group being distinctly more southern than the former. 



The 52 species found in Lewis and Harris include a few 

 which I had not expected to find, while several species did 

 not occur which I specially looked for. I have already 

 referred to the absence of H. inorio ; another species which 

 I certainly expected to find in some of the numerous lochs 

 was Ccelanibus novem-lineatus, Steph. I did not find it in 

 Eigg during my first visit there, but in the following year it 

 occurred in the Lochan na Beinn Buiddhe, the only loch 

 I examined ; ^ I did not find it in Skye during the few days 



' Record published by Donisthorpe, " Coleoptera on the Isle of 

 Eigg," Ent. Rec, 19 12, pp. 13, 14. 



