8 4 
MR. CHAS. D. SOAR ON THE HYDRACHNIDS 
Biological Laboratory, has during the last year kept me well 
supplied with mites preserved in formalin, with records of 
dates and localities. These mites have all had my attention 
as time allowed and the present list is the result. I call it 
simply a preliminary paper, because I believe a great many 
more species are yet to be found in a district so well adapted 
for fresh water life of all kinds, teeming as it is in all its waters 
with vegetable and animal forms. 
In the British Isles at present we have about 150 species 
representing thirty-seven different genera. In this paper 
which represents the Norfolk Broads only, we have seventy- 
one species representing twenty- two genera. Two species 
only are new records for Britain, but there are about six 
species I have not yet been able to identify, and these may 
turn out something new. If so, they will be described in 
the next paper. 
To judge by our present knowledge of the Hydrachnidae, 
their life-cycle appears to occupy about three years. This 
being so, there is every reason to suppose that another year’s 
collecting would bring in several species which do not figure 
in this list. The eggs are generally deposited on the under 
side of the leaves of water plants, Anacharis being a favourite 
plant for that purpose. In some cases the eggs are found 
floating about in small batches near the bottom or on the 
mud, enveloped in a gelatinous film. All mites, I believe, 
are oviparous. The time the eggs take to develop varies 
with the genera, and no doubt is also much influenced by 
the temperature and environment to which they are subjected 
at the time, and eggs which have taken twenty days in a 
small glass tank in a warm room would, perhaps, take twenty- 
five in a lake. Those that I have watched develop at home 
have taken from twelve to thirty-nine days, according to 
the genera to which they belonged. For instance, Fiona took 
twelve days, Arrhenurus twenty-four, Eulais thirty-eight, 
and Limnesia thirty-nine. The larvae which hatch from the 
eggs are hexapod, and they soon become parasitic. No 
doubt each species has its own particular host which it seeks 
and to which it attaches itself as soon as possible. It is this 
