Palaeosomatides (Palaeosomata, Bifemorata)

Superorder Acariformes

   Order Sarcoptiformes

      Suborder Oribatida

          Supercohort Palaeosomatides (Archeonothroidea, Palaeacaroidea, Ctenacaroidea)

 

Common names: palaeosomate oribatid mites

 

Probability of Encounter: low

 

Quarantine importance: No known quarantine importance.

 

Diagnosis.  White to tan, sack-like oribatid mites usually with long black setae and weakly expressed plates.  Chelicerae visible from above; usually with small naso, rarely bearing median eye(s) on its underside.  Subcapitulum with 3 pairs of adoral and 4 pairs of subcapitular setae; rutella simple.  Femora I-IV of tritonymphs and adults divided; tarsi bidactyl or tridactyl in immatures and adults.  Opisthosomal glands absent.  Macropyline; 3 pairs of genital papillae, often on segmented stalks.

 

Similar mites.  Astigmatina, Parhyposomatides, and juveniles of other groups of Oribatida often have sac-like bodies, but these mites usually have opisthosomal glands, never have median eyes, and do not have divided femora.

 

Ecology & Distribution. Palaeosomatans are found worldwide in many soil types, but seem to be especially characteristic of dry soils.  Species of Aphelacarus also are found in house dust.  They are thought to be the most primitive extant Oribatida.  Although relatively common in grassland, open forest and sandy soils, these mites are usually missed or misidentified because of their small size, lack of sclerotization, slender setae, and general similarity to immature oribatids or astigmatans.  The genera found in forest soils (e.g. Stomacarus, Loftacarus, Palaeacarus), however, are larger and have long, black, erectile setae and are more noticeable.

 

References

Balogh J & Mahunka S.  1985.  Primitive Oribatids of the Palaearctic Region.  Elsevier: Amsterdam.

Bulanova-Zachvatkina, E.M. 1980.  On the Palaeosomata (Acariformes, Oribatei) of the U.S.S.R.  Entomol. Oboz. 59:  679-688.

Colloff M & Halliday B.  1998.  Oribatid Mites.  A Catalogue of Australian Genera and Species.  Monograph on Invertebrate Taxonomy Vol. 6.  CSIRO Publications: Melbourne.

Gilyarov MS & Krivolutsky DA (eds)  1975.  Handbook for the Identification of Soil-inhabiting Mites, Sarcoptiformes.  Zoological Institute of the Academy of Sciences: Petrograd [In Russian]

Hunt G, Colloff MJ, Dallwitz M, Kelly J. & Walter DE.  1998.  An Interactive Key to the Oribatid Mites of Australia.  CSIRO Publishing, Collingwood, Victoria.  (Compact Disk and User Guide).

Krantz GW.  1978.  A Manual of Acarology.  OSU Bookstores: Corvallis.

Lee DC. 1981. Sarcoptiformes (Acari) of South Australian soils. 1. Notation. 2. Bifemorata and Ptyctima (Cryptostigmata). Records of the South Australian Museum 18 : 199-222.

Norton RN.  1990.  Oribatida.  pp. 779-803, in DL Dindal (ed) Soil Biology Guide.  John Wiley & Sons: Brisbane.