Taxonomic Position

Cohort Microgyniina,

    Superfamily Microgynioidea

Microgyniidae (Microsejidae)

    Microsejus Trägårdh

 

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 in key.  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.

 

Similar taxa not in key.  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 & Distribution.  Microsejus truncicola Trägårdh is the only knowns species and is associated with tree stumps in boreal forests.   The deutonymph is phoretic.

 

References

Evans EO and 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 MS & Bregatova NG (eds)  1977.  Handbook for the Identification of Soil-inhabiting Mites, Mesostigmata.  Zoological Institute of the Academy of Sciences: Petrograd [In Russian]

Johnston, D.E.  1982.  Mesostigmata.  In: Parker, S.P. (ed.)  Synopsis and classification of living organisms.  McGraw-Hill, New York, p. 112-116.

Krantz, G. W.  1961.  A re-evaluation of the Microgynioidea, with a description of a new species of Microgynium (Acarina: Mesostigmata).  Acarologia 3: 1-10.

Walter, D.E. and Krantz, G.W.  1999.  New early derivative mesostigmatans from Australia: Nothogynus, n. g., Nothogynidae, n. fam. (Mesostigmata: Microgyniina).  International Journal of Acarology 25: 67-76.