131 
THE AQUATIC COLEOPTERA OF THE ISLE OF MAN, 
WITH SOME REMARKS ON THE ORIGIN OF THE 
FAUNA. 
FRANK BALFOUR BROWNE, M.A.(Oxon.), F.R.S_E., F.Z.S. 
In his vice-presidential address before the Lancashire and 
Cheshire Entomological Society*, the late Dr. J. Harold 
Bailey discussed the coleoptera of the Isle of Man, and gave his 
opinion as to the origin of that part of the Manx fauna. He 
said: ‘The Manx coleoptera fauna is derived, as regards 
the majority of its species, from migrations across former 
land-connections both from England and Ireland; the Irish 
element passing along the Irish-Welsh bridge which was.the 
first to disappear, the great mass of the species reaching the 
island from land to the east and south, the last bridge to exist 
being to the coasts of Lancashire and Cumberland.’ 
This statement as to the origin of the Manx coleoptera has 
become the more interesting to me the farther my researches 
into’ the ipresent distribution of the Britannic water-beetles 
has led me, and I have been able, during the past season to 
spend some ten days in the Isle of Man investigating the water- 
beetle fauna which has,:as Dr. Bailey mentions, been almost 
neglected so far. I wasmot only able to collect a large number 
of species myself, but I learnt that Dr. Bailey’s collection of 
beetles was in the possession of the Isle of Man Antiquarian 
and Natural History Society, and, owing to the kindness of 
Dr. Cassal, the custodian of the collection, I was allowed to 
examine the water-beetles, and so add to my knowledge of the 
species found in the island. I learn from Dr. Bailey’s address 
that the Dale collection at Oxford contains some Manx beetles, 
but: have not so far been able to look through the water 
beetles of that collection. 
I propose in the present paper to describe the results of my 
researches, and also to discuss shortly the origin of the fauna, 
so far as the water beetles throw any light upon it. I have as 
usual, only included the Hydradephaga and Hydrophilidae, 
omitting the genera Spheridium, Cercyon, Megasternum and 
Cryptopleurum. 
With regard,to published records the Isle of Man apparently 
only boasts a fauna of nineteen species of water beetles, but, 
through the kindness of Dr. Bailey, Mr. W. E. Sharp and 
others, in sending me specimens or their lists of captures, I 
had accumulated a list of forty-two species. In Dr. Bailey’s 
collection I found fifty-two species, a few of which had been 
a ee ne ee ee 
* “31st Ann. Rep. and Proc. Lanc. and Cheshire Ent. Soc.,’ 1908, pp- 
39, 40. 
1g11 Maf. 1. 
