MM339999

Ascids are mites belonging to the suborder Mesostigmata of the Order Parasitiformes. The vast majority of parastiformans, including ticks (Ixodida), are terrestrial. However, a few genera in the Ascidae are sometimes found in aquatic situations. In Australia, ascids of the genus Cheiroseius have been found in water-filled treeholes (Kitching & Callaghan 1982). These mites appear to be amphibious, as we have observed them walking both under water and on the dry sides of containers (pers. obs., DEW, HCP). Ascids of the genus Platyseius are common inhabitants of marshy ground in Europe (Hinton 1971), and have been found in streams in Queensland (pers. obs. K. Dwine, DEW). Ascids are predators and will feed on nematodes and small arthropods, including their eggs.

Mesostigmatans may be differentiated from other mites by the presence of a bifurcate structure, the tritosternum, between the first pair of legs. Mesostigmatans are also characterised by having the openings to their respiratory tubes, the stigmata, on the sides of the body between the 2nd and 4th pairs of legs. Although Cheiroseius and Platyseius are the only known semi-aquatic mesostigmatans in Australia, other taxa of terrestrial mesostigmatans may appear in aquatic samples when they fall into the water and drown.

References:

Hinton, H.E. 1971. Plastron respiration in the mite, Platyseius italicus. J. Insect Physiol. 17: 1185-1199.

Kitching, R.L. and C. Callaghan. 1982. The fauna of water-filled treeholes in box forest in south-east Queensland. Australian Entomological Magazine 8: 61-70.

Krantz, G.W. 1978. A Manual of Acarology. 2nd edition. Oregon State University Book Stores, Corvallis, Oregon.

Walter, D.E. and H.C. Proctor. 1999. Mites: Ecology, Evolution and Behaviour. University of New South Wales Press, Sydney, New South Wales.