SOAR : WATER MITES OF EPPING FOREST. 97
The Acarina have not as yet been treated fully by many
writers. There is still, therefore, a large field open for those
who will make a study of these minute and interesting creatures.
Mr. A. D. Michael, F.L.S., when engaged on his great work on
the British Oribatida, one of the families of the Acarina, care-
fully worked the forest for specimens, but I believe that he
published no special list of the Oribatidae he found.
1 am chiefly interested in one sub-order of the Acarina,
namely the Hydracarina, and now propose to give a list of
these found in collections made in the Forest during a period
of about twenty years. Living, as I do, on the other side of
London, I have not been able to visit the Forest as often as I
have wished. Nevertheless, I believe I have worked syste-
matically the whole of the ponds In the Forest from Wanstead,
in the south, to the Lower Forest, about Epping, in the north.
Independently of the collections made by myself, I have had a
great deal of help from members of the Royal Microscopical
Society, the Quekett Club, and the Essex Field Club, who
have continually supplemented my records with their own.
The localities given in the accompanying list must be under-
stood as indicating districts only, and not merely the actual
place of collecting. For instance, Snaresbrook includes, not
only the Eagle Pond, but all the ponds within reach during
a ramble from Snaresbrook station by way of Gilbert's Slade
to George Lane.
Although so many collections have already been made in
the Forest, and the species found identified, there is no doubt
that more mites are still waiting to be recorded; for the fauna of
ponds is continually changing. The following list (which is, I
believe, quite reliable as far as it goes) will serve, however, as a
basis for future work.
Since Koch's time, several systems of classification have
been proposed, and more or less improved on from time to time.
The system of classification and nomenclature used here will be
on Koenike's plan.
The Hydracarina is a sub-order of the order Acarina. In
Koenike's last classification, it is divided into five families—
Limnocharidae, Eylaidae, Hydryphantidae, Hydrachnidae, and
Hygrobatidae. So well marked are the features of this sub-
order that the animals comprised in it cannot well be mistaken