Taxonomic Position

Cohort Gamasina

    Subcohort Dermanyssiae

  Superfamily Phytoseioidea

 

Family: Blattisociidae

Zercoseius Berlese

 

Diagnostic characters:

• Blattisociidae with extensive dorsal and ventral sclerotization

• Dorsal shield with 39 pairs of setae, lacking setae z1, s1-2, r2;  R-series reduced to one seta (R1); most dorsal setae strongly pilose, some +/- tricarinate-pilose, some posterior-marginal dorsal shield setae (S4-5, Z5) pilose and clubbed to spatulate; genital shield subtrapezoidal with stp4 on postero-lateral margins.

Ecology & Distribution. Species of Zercoseius are rare soil-inhabiting mites.

Similar taxa.  Species of Arrhenoseius have the metapodal elements fused to the peritrematal shield and do not have clubbed to spatulate setae.

Key to Genera of Blattisociidae

1.   Leg II of female often thickened, with strong, opposable spine-like setae on ventral surface on femur, genu, tibia, and tarsus; fixed chela multidentate, its distal extremity usually with enlarged rounded margin bearing a row of small rasping teeth; trochanter I with 4 or 5 setae (av1 absent); genu and tibia I each with maximum of 11 setae (pd3, av2 absent)........................................................ Hoploseius

-      Leg II of female not thickened, without spine-like ventral setae; fixed chela with few to many teeth, its distal extremity not enlarged, without row of small teeth; trochanter I with 6 setae (av1 present); genu and tibia I each with 13 (rarely 12) setae (pd3 and usually av2 present)............................................ 2

2.   Corniculi narrowly separated, usually slender; epistome convex, smooth; fixed chela with few or no teeth; peritrematal shield slender, barely wider than stigma at level of stigma; female with humeral seta (r3) usually on soft cuticle beside dorsal shield; protonymph with 2 setae on palp trochanter.....3

-      Corniculi well separated, stout; epistome convex or triramous, smooth or denticulate; fixed chela usually with many teeth; peritrematal shield clearly wider than diameter of stigma at level of stigma; female with humeral setae on dorsal shield; protonymph with 1 seta on palp trochanter.........................4

3.   Dorsal shield without midlateral incisions; opisthonotal region of dorsal shield holotrichous, with 15 pairs of setae; fixed chela well developed or reduced; female without isolated metasternal plates; male leg IV without enlarged, spine-like setae ............................................................ Blattisocius

-      Dorsal shield with midlateral incisions; opisthonotal region of dorsal shield hypotrichous, with 12 pairs of setae (lacking a pair in each of J, Z, S series); fixed chela well developed; female with isolated metasternal plates; male leg IV with several enlarged spine-like setae .... Adhaerenseius

4.   Female and male with all marginal r-R setae on edge of dorsal shield, opisthonotal region of shield with 20 pairs of setae; rows of deutosternal denticles narrow, each with 2-4 denticles; movable chela with ridge extending from para-axial surface to 1-2 denticles on proximo-ventral surface....Orthadenella

-      Female and male with 1-9 pairs of marginal r-R setae on soft cuticle beside dorsal shield, opisthonotal region of shield with maximum of 15 pairs of setae in female, 17 in male; rows of deutosternal denticles moderately wide, each with 5 to many denticles; movable chela lacking ridge or denticles on paraxial and ventral surface ............................................................................................................ 5

5.   Adults with 1 pair of marginal setae (R1) on soft lateral cuticle; female metapodal plates incorporated into ventrianal or peritrematal plates, and ventrianal shield with 7 pairs of setae in addition to circumanals; male with holoventral shield. ............................................................................................... 6

-    Adults with 3-9 pairs of marginal setae (r-R) on soft lateral cuticle; female metapodal plates free on soft cuticle, and ventrianal shield with 6 or fewer pairs of setae in addition to circumanals; male usually with separate sternogenital, ventrianal and peritrematal-exopodal shields ..................................7

6.   Podonotal region of adult dorsal shield lacking setae z1, s1, s2; female with metapodal plates incorporated into ventrianal shield; female ventrianal shield lacking setae ZV1 but with JV5 on its posterolateral margins; genu III with 10, tibiae III and IV with 9 and 10 setae, respectively (pl-2 present on each of these segments) .................................................................................................... Zercoseius

-      Podonotal region of adult dorsal shield holotrichous; female with metapodal plates incorporated into posterior margins of peritrematal shields; female ventrianal shield with setae ZV1 but with JV5 inserted on soft cuticle behind its posterolateral margins; genu III with 9, tibiae III and IV with 8 and 9 setae, respectively (pl-2 absent from each of these segments) .......................................................... Arrhenoseius

7.   Female with 11 pairs of setae on podonotal region of dorsal shield (s5 absent) and 7-10 pairs of setae on opisthonotal region (Z1, J2 absent); epigynial shield rounded posteriorly; ventral setae ZV1, JV5 absent; cervix of spermatheca not sclerotized; movable chela with 4 teeth; genua II and III with 10 and 8 setae respectively (pv1 absent) ........................................................................................ Aceodromus

-      Female with 12-23 pairs of setae on podonotal region of dorsal shield (s5 present) and 10-15 pairs of setae on opisthonotal region (Z1, J2 present); epigynial shield usually truncate posteriorly; ventral setae ZV1, JV5 present; cervix of spermatheca well sclerotised; movable chela with 3 teeth (rarely 4); genua II and III usually with 11 and 9 setae respectively (pv1 usually present).............................Lasioseius

 

References

Evans GO & 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.

Halliday RB, Walter DE & Lindquist EE.  1998.  Revision of the Australian Ascidae (Acarina: Mesostigmata).  Invertebrate Taxonomy 12: 1-54.

Karg W. 1993. Acari (Acarina), Milben. Parasitiformes (Anactinochaeta). Cohors Gamasina Leach. Raubmilben. (Second Edition). Die Tierwelt Deutschlands 59: 1-523.

Krantz GW & Ainscough B.  1990.  Mesostigmata.  pp. 583-665, in DL Dindal (ed) Soil Biology Guide.  John Wiley & Sons: Brisbane.

Lindquist EE & Evans GO. 1965. Taxonomic concepts in the Ascidae, with a modified setal nomenclature for the idiosoma of the Gamasina (Acarina : Mesostigmata). Memoirs of the Entomological Society of Canada 47: 1-64.

Walter DE. & Lindquist EE.  2001.  Arrhenoseius gloriosus n. g., n. sp. (Acari: Mesostigmata: Ascidae), an arrhenotokous mite from rainforests in Queensland, Australia.  Acarologia 41: 53-68.