Taxonomic Position

Cohort Gamasina

    Subcohort Dermanyssiae

  Superfamily Ascoidea

Family: Ascidae Voigts & Oudemans

Subfamily: Ascinae

Diseius Lindquist & Evans (one described species, D. ulmi (Hirschmann))

 

Diagnostic characters:

• Completely divided dorsal shield without transverse lines extending across surface

• Podonotal shield with 13 pairs of setae (j2, z1-3 absent; s1-2, r2-5 in soft cuticle laterad shield)

• Opisthonotal shield with 12 pairs of setae (J3, Z2, S1 absent), R1-5 in soft cuticle

• Small anal shield with only circumanal setae, paranal setae inserted closer to posterior margin of anus than to anterior margin

• Genu and tibia I with only 4 dorsal setae; genu IV with 7 setae (pl1 present; al2, pd3 absent); tibia IV with 7 setae (al2, pl2, pd3 absent)

• Sternal pore 3 on sternal shield; setae Z5 whip-like

• Gnathotectum rounded, denticulate.

Ecology & Distribution.  These mites are poorly known inhabitants tree bark.

Similar taxa not in Lucid key (see below): See key to small Rhodacarus-like mites.

Synonymies.  Iphidozercon ulmi Hirschmann, Leioseius ulmi (Hirschmann)

Similar taxa in key. Gamasellodes Athias-Henriot, Protogamasellus Karg

 

Key to genera in the subfamily Ascinae

 

1.  With holodorsal shield that captures the R-series ..... 2

-   Dorsal shield divided into two subequal shields; R-series setae in soft cuticle ..... 3

2.  Seta z1 present laterad seta j1 on anterior median region of dorsal shield; femur III with 7 setae; genu I with 13 setae; tibia II with 10 setae ..... Orthadenella (Blattisociidae)

-    Seta z1 absent; femur III with 6 setae; genu I with 12 setae; tibia II with 9 setae ..... Neojordensia

3.   Opisthonotal shield with 12 pairs of setae (J3, Z2, S1 absent); podonotal shield lacking setae j2, z1, z3; adult leg setation strongly neotenous, genua I-II-III-IV with 11-8-7-7 setae, tibiae with 11-7-7-7 setae; female with anal shield ..... Diseius

-     Opisthonotal shield with 15 or more pairs of setae (J3, Z2, S1 present); podonotal shield with setae j2, z3, sometimes z1; adult leg setation not strongly neotenous, minimum number of setae on genua 12-11-8-8, on tibiae 13-10-8-9; female with anal or ventrianal shield ..... 4

4.   Hypostome with corniculi bifid apically; anterior rostral setae thickened, spinelike; dorsal shield setae z1 absent  ..... Anephiasca

-    Hypostome with corniculi entire apically; anterior rostral setae of similar thickness to other hypostomal setae; dorsal shield setae z1 present or absent ..... 5

5.   Female with epigynial shield strongly rounded posteriorly and with small subtriangular ventrianal or anal shield bearing 3-5 setae; male with ventrianal shield united to peritrematal shields; soft body cuticle often with microtuberculate striae ..... 6

-     Female with epigynial shield truncate posteriorly and usually with well developed ventrianal shield (rarely anal shield) bearing 3-9 setae (including circumanal setae); male with ventrianal shield separate from peritrematal shields; soft body cuticle striae without microtubercles ..... 8

6.   Palps elongated, at least half as long as leg I; palp trochanter longer than femur; palp tibia almost 3 times as long as tarsus ..... Anystipalpus

-     Palps of normal length, about one-third as long as leg I; palp trochanter slightly shorter than femur; palp tibia twice as long as tarsus ... 7

7.   Legs I with ambulacra and claws ..... Antennoseius (Vitzthumia)

-     Legs I with out ambulacra and claws ..... Antennoseius (Antennoseius)

8.    Opisthonotal shield with setae Z4 & S5 usually approximate and inserted together on pair of prominent posterolateral tubercles; podonotal shield lacking setae z1,  j2 well behind level of j1; peritrematal shields of adults broad, truncate posteriorly; genu I with 12 setae (av2 absent) ..... Asca

-     Opisthonotal shield with setae Z4, S5 well separated, not borne on pair of strong tubercles; podonotal shield with setae z1 present; j2 tending to be displaced anteriorly, often in approximately transverse row with z1 and j1; peritrematal shields of adults narrow or of moderate width, tapering posteriorly; genu I with 13 setae (av2 present) ..... 9

9.      Podonotal shield with transverse line extending across surface at level of setae z6, opisthonotal shield with similar line at level of setae J1; paranal setae inserted close to anterior margin of anus; genu IV with 8 setae (pl1 absent); tibia IV with 9 setae (pl2 absent) ..... Protogamasellus

-        Dorsal shields without transverse lines extending completely across surface; paranal setae inserted closer to posterior margin of anus than to anterior margin; genu IV with 9 setae (pl1 present); tibia IV with 10 setae (pl2 present) ..... 10

10.      Sternal pore 3 in soft cuticle; setae r3 and Z5 club-shaped, densely plumose; gnathotectum denticulate; movable digit of chelicerae serrate ..... Ectoantennoseius

-        Sternal pore 3 on sternal shield; setae r3 and Z5 setiform, smooth to barbed; gnathotectum more or less smoothly trifurcate; movable digit of chelicerae usually with 4-6 teeth, not serrate ..... Gamasellodes

 

References

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

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.