AUSTRALIAN ACARINA 
THE GENERA BRACHYCHTHONIUS BERL. AND 
COSMOCHTHONIUS BERL. (HYPOCHTHONIDAE- 
ORIBATOIDEA) 
By H. WOMERSLEY, F.R.E.S., A.L.S., ENTOMOLOGIST, 
SOUTH AUSTRALIAN MUSEUM 
Summary 
The species of the genera dealt with in this paper are very small, colourless to yellow 
mites found inhabiting moss. Owing to their small size, under 0.30 mm. in length, 
special methods of collecting are required, generally by putting the moss through the 
special funnel invented by Berlese, Hitherto the genera have not been recorded from 
Australia, but recently in samples of moss brought back from Normanville 
(September, 1943) and Quorn, South Australia (November, 1943), I have found 
representatives of five species of which three can probably be referred to European 
forms, the others being new. The specific characters of these small mites, of which 
about a dozen species are described, are found in the presence or absence of dorsal 
sculpturing, and when present its nature, and more particularly in the structure and 
comparative length of the sensillary or pseudostigmal setae, and of the normal dorsal 
setae. Unfortunately workers on this group have been content with comparing the 
lengths of the dorsal setae of the various species in general terms and not in actual 
dimensions. With such mites as these inhabiting moss, and of which both the mosses 
and the mites are extremely archaic and cosmopolitan, or widely spread by commerce, 
or both, it 1s extremely difficult to refer specimens to descriptions from other 
countries without access to authentic material, unless actual setal lengths are given. 
