Mesostigmata

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Taxonomy

updated 2025

Diagnostic characters

• Completely divided dorsal shielddivided dorsal shield:
  in Mesostigmata, adult mites have two usually subequal dorsal shields.
  
• Opisthonotal shieldopisthonotal shield:
  the posterior shield in mesostigmatans with divided dorsal shields.
  bearing setae Z4 and S5 usually approximateapproximate:
  close together, near, adjacent
  and inserted together on pair of prominent posterolateral tubercles
• Podonotal shieldpodonotal shield:
  the anterior shield in mesostigmatans with divided dorsal shields.  
  lacking setae z1, and with j2 well behind level of j1
• Peritrematalperitrematal:
  (peritrematic) of or referring to the peritreme; adjectival form of peritreme.
  shields of adults broad, truncate posteriorly; genugenu:
  (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
  I with 12 setae (av2 absent).

Similar taxa

Antennoseius Berlese, Ectoantennoseius Walter, Gamasellodes Athias-Henriot, Protogamasellus Karg, and Diseius Lindquist and Evans lack horns. Some Digamasellidae have horns, but also have sternal shields 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.
st4.

Key to genera in the subfamily Ascinae

1. With holodorsal shieldholodorsal shield:
   a shield that covers all of the dorsum.  In Mesostigmata, the holodorsal shield is often interpreted as resulting from the fusion of podonotal and opisthonotal shields and a suture between these regions is often visible (see recurved and procurved).
   that captures the R-series.............................. 2
   - Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield divided into two subequal shields; R-series 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.
   in softcuticle.............................. 3

2. Setaseta:
   (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.
   z1 present laterad setaseta:
   (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.
   j1 on anterior median region of dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield; femurfemur:
   (pl. femora) major leg segment between trochanter and genu; often subdivided into a basifemur and a telofemur.
   III with 7 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.
   ; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   I with 13 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.
   ; tibiatibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   II with 10 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.
   .............................. Orthadenella (Blattisociidae)
   - Setaseta:
   (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.
   z1 absent; femurfemur:
   (pl. femora) major leg segment between trochanter and genu; often subdivided into a basifemur and a telofemur.
   III with 6 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.
   ; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   I with 12 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.
   ; tibiatibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   II with 9 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.
   .............................. Neojordensia

3. Opisthonotal shieldopisthonotal shield:
   the posterior shield in mesostigmatans with divided dorsal shields.
   with 12 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.
   (J3, Z2, S1 absent); podonotal shieldpodonotal shield:
   the anterior shield in mesostigmatans with divided dorsal shields.  
   lacking 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.
   j2, z1, z3; adult leg setation strongly neotenous, genuagenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   I–II–III–IV with 11–8–7–7 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.
   , tibiaetibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   with 11–7–7–7 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.
   ; female with anal shield.............................. Diseius
   - Opisthonotal shieldopisthonotal shield:
   the posterior shield in mesostigmatans with divided dorsal shields.
   with 15 or more 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.
   (J3, Z2, S1 present); podonotal shieldpodonotal shield:
   the anterior shield in mesostigmatans with divided dorsal shields.  
   with 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.
   j2, z3, sometimes z1; adult leg setation not strongly neotenous, minimum number 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.
   on genuagenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   12–11–8–8, on tibiaetibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   13–10–8–9; female with anal or ventrianal shieldventrianal shield:
   in Mesostigmata, a ventral shield bearing the anal opening, circum anal setae, and one or more pairs of ventral setae or pores (lyrifissures) [see anal shield]; maybe rather narrow or very broad and covering most of the gaster.
   .............................. 4

4. Hypostome with corniculicorniculus:
   (pl. corniculi) (also, external malae) a usually horn-like process (sometimes toothed, bifurcate, trifurcate, spine-like, spatulate, or membranous) on the subcapitulum of parasitiform mites that usually supports the salivary styli.  A toothed corniculus could be confused with a rutellum, a possibly homologous structure in Acariformes and Opilioacarida. Phytoseiid image is spatulate corniculus.
   bifid apically; anterior rostral 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.
   thickened, spinelike; dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield 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.
   z1 absent.............................. Anephiasca
   - Hypostome with corniculicorniculus:
   (pl. corniculi) (also, external malae) a usually horn-like process (sometimes toothed, bifurcate, trifurcate, spine-like, spatulate, or membranous) on the subcapitulum of parasitiform mites that usually supports the salivary styli.  A toothed corniculus could be confused with a rutellum, a possibly homologous structure in Acariformes and Opilioacarida. Phytoseiid image is spatulate corniculus.
   entire apically; anterior rostral 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.
   of similar thickness to other hypostomal 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.
   ; dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield 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.
   z1 present or absent.............................. 5

5. Female with epigynialepigynal:
   (also epigynial) of or relating to the female genital opening or a shield protecting it.
   shield strongly rounded posteriorly and with small subtriangularsubtriangular:
   more or less triangular.  
   ventrianal or anal shield bearing 3–5 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.
   ; male with ventrianal shieldventrianal shield:
   in Mesostigmata, a ventral shield bearing the anal opening, circum anal setae, and one or more pairs of ventral setae or pores (lyrifissures) [see anal shield]; maybe rather narrow or very broad and covering most of the gaster.
   united to peritrematalperitrematal:
   (peritrematic) of or referring to the peritreme; adjectival form of peritreme.
   shields; soft bodybody:
   the idiosoma of mites.
   cuticle often with microtuberculate striaestriae:
   the raised, narrowly aligned cuticular ridges, often like a fingerprint or plicate pattern; striations.
   .............................. 6
   - Female with epigynialepigynal:
   (also epigynial) of or relating to the female genital opening or a shield protecting it.
   shield truncate posteriorly and usually with well developed ventrianal shieldventrianal shield:
   in Mesostigmata, a ventral shield bearing the anal opening, circum anal setae, and one or more pairs of ventral setae or pores (lyrifissures) [see anal shield]; maybe rather narrow or very broad and covering most of the gaster.
   (rarely anal shield) bearing 3–9 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.
   (including circumanal 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.
   ); male with ventrianal shieldventrianal shield:
   in Mesostigmata, a ventral shield bearing the anal opening, circum anal setae, and one or more pairs of ventral setae or pores (lyrifissures) [see anal shield]; maybe rather narrow or very broad and covering most of the gaster.
   separate from peritrematalperitrematal:
   (peritrematic) of or referring to the peritreme; adjectival form of peritreme.
   shields; soft bodybody:
   the idiosoma of mites.
   cuticle striaestriae:
   the raised, narrowly aligned cuticular ridges, often like a fingerprint or plicate pattern; striations.
   without microtubercles.............................. 8

6. Palps elongated, at least half as long as leg I; palp trochantertrochanter:
   the leg segment between the coxa and the femur.
   longer than femurfemur:
   (pl. femora) major leg segment between trochanter and genu; often subdivided into a basifemur and a telofemur.
   ; palp tibiatibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   almost 3 times as long as tarsustarsus:
   (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
   .............................. Anystipalpus
   - Palps of normal length, about one-third as long as leg I; palp trochantertrochanter:
   the leg segment between the coxa and the femur.
   slightly shorter than femurfemur:
   (pl. femora) major leg segment between trochanter and genu; often subdivided into a basifemur and a telofemur.
   ; palp tibiatibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   twice as long as tarsustarsus:
   (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
   .............................. 7

7. Legs I with ambulacra and claws.............................. Antennoseius (Vitzthumia)
   - Legs I without ambulacra and claws.............................. Antennoseius (Antennoseius)

8. Opisthonotal shieldopisthonotal shield:
   the posterior shield in mesostigmatans with divided dorsal shields.
   with 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.
   Z4 & S5 usually approximateapproximate:
   close together, near, adjacent
   and inserted together on pair of prominent posterolateral tubercles; podonotal shieldpodonotal shield:
   the anterior shield in mesostigmatans with divided dorsal shields.  
   lacking 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.
   z1,  j2 well behind level of j1; peritrematalperitrematal:
   (peritrematic) of or referring to the peritreme; adjectival form of peritreme.
   shields of adults broad, truncate posteriorly; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   I with 12 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.
   (av2 absent).............................. Asca
   - Opisthonotal shieldopisthonotal shield:
   the posterior shield in mesostigmatans with divided dorsal shields.
   with 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.
   Z4, S5 well separated, not borne on pair of strong tubercles; podonotal shieldpodonotal shield:
   the anterior shield in mesostigmatans with divided dorsal shields.  
   with 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.
   z1 present; j2 tending to be displaced anteriorly, often in approximately transverse row with z1 and j1; peritrematalperitrematal:
   (peritrematic) of or referring to the peritreme; adjectival form of peritreme.
   shields of adults narrow or of moderate width, taperingtapering:
   drawn out or with margins converging.
   posteriorly; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   I with 13 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.
   (av2 present).............................. 9

9. Podonotal shieldpodonotal shield:
   the anterior shield in mesostigmatans with divided dorsal shields.  
   with transverse line extending across surface at level 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.
   z6, opisthonotal shieldopisthonotal shield:
   the posterior shield in mesostigmatans with divided dorsal shields.
   with similar line at level 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.
   J1; paranal 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.
   inserted close to anterior margin of anus; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   IV with 8 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.
   (pl1 absent); tibiatibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   IV with 9 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.
   (pl2 absent).............................. Protogamasellus
   - Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shields without transverse lines extending completely across surface; paranal 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.
   inserted closer to posteriorposterior:
   the back part of the body or towards that region in comparison, e.g., 'posterior to'.
   margin of anus than to anterior margin; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   IV with 9 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.
   (pl1 present); tibiatibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   IV with 10 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.
   (pl2 present).............................. 10

10. Sternal porepore:
    a pore-like opening or structure in the cuticle.  In Mesostigmata, lyrifissures and true pore openings are often difficult to separate and both tend to be called 'pores', e.g., the sternal pores stp1-3.
    3 in soft cuticle; 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.
    r3 and Z5 club-shaped, densely plumose; gnathotectumgnathotectum:
    (= epistome, tectum) an often membranous dorsal projection of the anterior margin of the basis capitulum in Mesostigmata; often diagnostic at family-, genus- or species-levels; also often difficult to see without high magnification and good optics.
    denticulate; movable digit of chelicerae serrateserrate:
    with closely set teeth that resemble the cutting edge of a saw.
    .............................. Ectoantennoseius
    - Sternal porepore:
    a pore-like opening or structure in the cuticle.  In Mesostigmata, lyrifissures and true pore openings are often difficult to separate and both tend to be called 'pores', e.g., the sternal pores stp1-3.
    3 on sternal shieldsternal shield:
    a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
    ; 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.
    r3 and Z5 setiform, smooth to barbed; gnathotectumgnathotectum:
    (= epistome, tectum) an often membranous dorsal projection of the anterior margin of the basis capitulum in Mesostigmata; often diagnostic at family-, genus- or species-levels; also often difficult to see without high magnification and good optics.
    more or less smoothly trifurcatetrifurcate:
    split into three distally.
    ; movable digit of chelicerae usually with 4–6 teeth, not serrateserrate:
    with closely set teeth that resemble the cutting edge of a saw.
    .............................. Gamasellodes

References

• Athias-Henriot 1969Athias-Henriot 1969:
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• Champ 1966Champ 1966:
  Champ BR. 1966. Insects and mites associated with stored products in Queensland: 4. Acarina and Pseudoscorpiones. Queensland Journal of Agricultural and Animal Sciences 23: 197–210.
• 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.
• Halliday et al. 1998Halliday et al. 1998:
  Halliday RB, Walter DE, Lindquist EE. 1998. Revision of the Australian Ascidae (Acarina: Mesostigmata). Invertebrate Taxonomy 12: 1–54.
• Hurlbutt 1963Hurlbutt 1963:
  Hurlbutt HW. 1963. The genus Asca von Heyden (Acarina: Mesostigmata) in North America, Hawaii and Europe. Acarologia 5: 480–518.
• Karg 1993Karg 1993:
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  Kinnear A. 1991. Acarine communities of semi-arid soils from the Eastern Goldfields region of Western Australia. Pedobiologia 35: 273–83.
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  Kitching RL, Callaghan C. 1982. The fauna of water-filled tree holes in box forest in south-east Queensland. Australian Entomological Magazine 8: 61–70.
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  Krantz GW. 1962. Acari. Free-living Mesostigmata. II. The family Aceosejidae. Parc National de la Garamba - Mission H. de Saeger 34: 3–29.
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  Krantz GW. 1986. A manual of acarology [2nd ed., emended 1986]. Oregon State University Book Stores, Corvallis.
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  Krantz GW, Ainscough B. 1990. Mesostigmata. pp. 583–665. In: Dindal DL, ed. Soil biology guide. John Wiley & Sons, Brisbane.
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  Lindquist EE. 1963. A taxonomic review of the genus Hoploseius Berlese (Acarina: Blattisocidae). The Canadian Entomologist 95: 1175–85.
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• Lindquist and Walter 1989Lindquist and Walter 1989:
  Lindquist EE, Walter DE. 1989. Biology and description of Antennoseius janus, new species (Mesostigmata: Ascidae), a mesostigmatic mite exhibiting adult female dimorphism. Canadian Journal of Zoology 67: 1291–1310.
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  Walter DE. 1987. Life history, trophic behavior and description of Gamasellodes vermivorax n. sp. (Mesostigmata: Ascidae) a predator of nematodes and arthropods in semiarid grasslands. Canadian Journal of Zoology 65: 1689–1695.
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