Endeostigmata

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Taxonomy

Oehserchestidae Kethley, 1977 (=Hybalicidae Theron, 1974Theron, 1974:
Theron PD. 1974. Hybalicidae, a new family of endeostigmatic mites (Acari: Trombidiformes). Acarologia 16: 397-412.)

Diagnosis

Prodorsumprodorsum:
the dorsal surface of the propodosoma.
with 1 pair of filiform trichobothriatrichobothrium:
(pl. trichobothria) (= bothridial sensillum) an often elaborately modified seta set in a cup-like base; forms include filiform, ciliate, pectinate or variously thickened or clubbed (bat-like to globose or capitate).
(bo) and 4 pairs of setaeseta:
(pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
(exp absent); naso well developed and bearing setaeseta:
(pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
ro; median eye absent, lateral eyes present or absent. Subcapitulumsubcapitulum:
(also infracapitulum) the venter of the capitulum; the ventral faces of the fused palpcoxae; apparently formed independently in the two superorders of mites.
with 5–6 pairs of setaeseta:
(pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
; rutellarutellum:
(pl. rutella) In Sarcoptiformes, the hypertrophied setae on the hypostome, often toothed; not to be confused with a corniculus (although possibly a homologue).  In Astigmata, the rutellum may be referred to as a pseudorutellum, although it is the same structure.  Various forms of rutella are recognized, including the atelebasic and pantelebasic.
well developed, dentate; chelicerae chelate-dentatechelate-dentate:
pincer-like chelicerae with teeth.
, each with 2 setaeseta:
(pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
. Opisthosomalopisthosomal:
(opisthosomatic) adjectival form of opisthosoma.
segment C with 3 pairs of setaeseta:
(pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
(c2 seemingly absent); segment sometimes PA absent; setaeseta:
(pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
dendritic, globoseglobose:
spherical.
, or pilosepilose:
with a covering of hairs or hair-like processes.
; 3 pairs of genital papillaegenital papillae:
 1-3 pairs of extrusible finger-like to button-like projections, usually retracted into in the genital vestibule of acariform mites; sometimes formed as sessile disks around the genital opening; thought to be osmoregulatory structures; modified or multiplied and dispersed over the body in many freshwater mites.  Genital papillae are absent in the larva, but may be added ontogenetically: protonymphs have one pair, deutonymphs two pairs, and tritonymphs (and adults) three pairs.  The tritonymphal pair of papillae is often lost.  The serially homologous Claparède's organ is usually present in the larvae (and prelarvae) of mites exhibiting genital papillae in nymphs and adults (Oudeman's Rule).
; 7–9 pairs of genital setaeseta:
(pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
; ovipositorovipositor:
an extrusible organ for laying eggs.  Female oribatids have a well developed ovipositor that ends in three finger-like projections.  Ovipositors are less well developed or absent in other mites.
, eugenital setaeseta:
(pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
present. Pretarsustarsal apotele:
(also pretarsus) the most distal segments of legs and palps bearing the claws and empodium
I without lateral claws, empodiumempodium:
(pl. empodia) an unpaired structure arising between the tarsal claws, ranging from pad-like to claw-like and often bearing structures such as tenent hairs, dense setulae, or taking the form of a featherclaw (Eriophyoidea)..
small, clawclaw:
like - having a distal hook; resembling a claw.
-like; pretarsi II-IV with unequal claws and clawclaw:
like - having a distal hook; resembling a claw.
-like empodiumempodium:
(pl. empodia) an unpaired structure arising between the tarsal claws, ranging from pad-like to claw-like and often bearing structures such as tenent hairs, dense setulae, or taking the form of a featherclaw (Eriophyoidea)..
; coxae I-IV contiguous; coxae IV apparently modified for jumping. Gut boluses with fungal hyphae and spores. Males unknown.

Remarks

These mites resemble truncate, globular Terpnacarus and the dorsaldorsal:
relating to the upper or back side; opposed to ventral.
setae resemble those on some Nanorchestes. The single pair of sensillasensillum:
(pl. sensilla) (also sensillae; 'sensillus' is incorrect) a sensory structure;  sensilla is often used for the bothridial seta in Acariformes.
, paired claws on legs II–IV, and lack of a strongly sclerotised labrum serve to separate Oehserchestes from Nanorchestes; Terpnacarus have paired claws and an empodiumempodium:
(pl. empodia) an unpaired structure arising between the tarsal claws, ranging from pad-like to claw-like and often bearing structures such as tenent hairs, dense setulae, or taking the form of a featherclaw (Eriophyoidea)..
on tarsustarsus:
(pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
I and prodorsal seta in. The gut contents have boluses composed primarily of fungal material. Coxae IV are modified for jumping.

References

• Kethley 1977bKethley 1977b:
  Kethley JB. 1977b. The status of Hybalicus Berlese, 1913 and Oehserchestes Jacot, 1939 (Acari: Acariformes: Endeostigmata). Fieldiana Zoology 72 (4): 59-64.
• Kethley 1982dKethley 1982d:
  Kethley JB. 1982d. Endeostigmata. pp. 118-120. In: Parker SP, ed. Synopsis and classification of living organisms, Vol. 2. McGraw-Hill, New York.
• Kethley 1990aKethley 1990a:
  Kethley JB. 1990a. Acarina: Prostigmata (Actinedida). pp. 667-756. In: Dindal DL, ed. Soil biology guide. John Wiley & Sons, Brisbane.
• Theron 1974Theron 1974:
  Theron PD. 1974. Hybalicidae, a new family of endeostigmatic mites (Acari: Trombidiformes). Acarologia 16: 397-412.