6o THE SCOTTISH NATURALIST 



THE AQUATIC COLEOPTERA OF THE 

 OUTER HEBRIDES. 



By Frank Balfour Browne, M.A. (Oxon. et Cantab.), 



F.R.S.E., F.Z.S. 



{Continued from page 20.) 



For instance, the average number of species per collection in 

 both Skye and Eigg was 61, and in Coll 5-9, so that, in spite 

 of the fact that these collections were made in other years and 

 in other months, the results agree. If, encouraged by these 

 results, we carry our comparisons farther afield, we find that 

 the farther we go south and east the richer become the 

 collections, quite apart from the actual number of species 

 found in the district. Thus in Clare Island only 47 species 

 occurred, but the average number of species per collection 

 was 7-5 ; while in Forfar, with 63 species, the average was 

 practically the same as in the Isle of Man, with 82 species. 

 East Norfolk, with about the same number of species as the 

 Isle of Man, had an average per collection of 13-5 in June and 

 1 8- 1 in September; while Cambridge, with 105 species in June 

 last, had an average of 19-4. The number of species in the 

 richest collection also increases markedly eastward and 

 southward ; and while the best collection in Lewis only 

 produced 16 species, the southern and eastern places produced 

 well over 20, while one collection in Cambridge even produced 

 41 species — more species, that is, than there are on the island 

 of Eigg ! 



But here again the comparison is somewhat misleading, 

 because I find that collections tend to run richer in one year 

 than in another. Thus in East Norfolk in 1904 five 

 collections each produced 30 or more species ; in the same 

 district in 1905 ten collections produced 30 or more species 

 (one 41, one 38, and one 36), while in the following year only 

 one collection produced over 30 species 1 The present year 

 has been, both in Cambridgeshire and West Norfolk, very 



