Mesostigmata

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Taxonomy

updated 2025

Diagnostic characters

• Brownish, subrectangular mites with podonotal, 2 mesonotal and pygidial shields
• Sternal shield divided, st1–2 and st3–4 on separate halves; genital shield with broad wings and a single pair of setae.
• Intercalary sclerite of tarsus IV reduced to linear remnant; setae av4 and pv4 absent.
• Trochanter I of adult with 5 setae; femora, genua and tibiae I with 10 setae; tibiae II–IV with 9 setae (2–1/1,2/1–2).
• Hypostomal setae in triangular array; palp apotele 2-tined; movable digit of chelicerae without excrescences.
• Males with sternal-genital shield bearing 4 pairs of setae; genital opening between coxae III; fifth pair of sternal setae on or near a separate plate between coxae IV.

Similar taxa

Microgynium has 4 setae on trochanter I, a single mesonotal shield, and has cheliceral excrescences. Nothogynus have nude mesonotal scutella and pygidial shields, 4-segmented palps, and lack claws on tarsus I. Polyaspidids have a nude genital shield. Saprosecans (Halolaelapidae) have posterior opisthonotal horn-like processes.

Taxon not in this tool: Davacarids have 3 genital shields, short peritremes, a lobe-like process on the chelicerae, and setae av4/ pv4 on tarsi IV. Sejids have setae av4/pv4.

Ecology and distribution

Microsejus truncicola Trägårdh is the only known species and is associated with tree stumps in boreal forests. The deutonymph is phoretic.

References

• Evans and Till 1979Evans and Till 1979:
  Evans EO, Till WM. 1979. Mesostigmatic mites of Britain and Ireland (Chelicerata: Acari-Parasitiformes): An introduction to their external morphology and classification. Transactions of the Zoological Society of London 35 (2): 145–270.
• Gilyarov and Bregatova 1977Gilyarov and Bregatova 1977:
  Gilyarov MS, Bregatova NG, eds. 1977. Handbook for the identification of soil-inhabiting mites, Mesostigmata. Zoological Institute of the Academy of Sciences, Petrograd.
• Johnston 1982bJohnston 1982b:
  Johnston DE. 1982b. Mesostigmata. pp. 112–116. In: Parker SP, ed. Synopsis and classification of living organisms, Vol. 2. McGraw-Hill, New York.
• Krantz 1961Krantz 1961:
  Krantz GW. 1961. A re-evaluation of the Microgynioidea, with a description of a new species of Microgynium (Acarina: Mesostigmata). Acarologia 3: 1–10.
• Walter and Krantz 1999Walter and Krantz 1999:
  Walter DE, Krantz GW. 1999. New early derivative mesostigmatans from Australia: Nothogynus, n. g., Nothogynidae, n. fam. (Mesostigmata: Microgyniina). International Journal of Acarology 25: 67–76.