Mesostigmata

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Taxonomy

updated 2025

Diagnostic characters

• Dorsaldorsal:
  relating to the upper or back side; opposed to ventral.
  shield well sclerotized, entireentire:
  a shield or sclerite with a continuous margin without incisions.
  or incised, ornamented with tubercles and bearing <25 pairs of often elongate, thickened and barbed 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.
  , 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.
  J5 absent
• Sternal shieldsternal shield:
  a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
  often reduced to 2 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.
  , st3 on shield or on platelets
• 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.
  distally toothed, chisel-like, or weakly membranous
• Chelicerae with membranous lobe
• Tectumgnathotectum:
  (= 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.
  simple, smoothly subtriangularsubtriangular:
  more or less triangular.  
  to acuminate, often with a well-developed median spine
• Genugenu:
  (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
  II with 2 ventral 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.
  
• Palp apotelepalptarsal apotele:
  (= palp apotele, palptarsal claw) the most distal segment of the palp; absent in Acariformes, claw-like in Opilioacarida, and a subdistal, tined structure in the Mesostigmata.
  3-tined
• Tarsustarsus:
  (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
  I with claws and 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)..
  

Similar taxa

Within the Ameroseiidae, species of Epicriopsis are most likely to be confused with those in Ameroseius that have relatively long 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.
; however, species of Ameroseius have 29 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.
on the dorsaldorsal:
relating to the upper or back side; opposed to ventral.
shield, as opposed to 24 or fewer in Epicriopsis. Dorsaldorsal:
relating to the upper or back side; opposed to ventral.
shield hypotrichy is also present and tubercular ornamentation is also characteristic of Podocinidae and Epicriidae.

Key to adult females of soil/nest inhabiting genera

1. Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield with marginal ring of tubercles 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.
   j5, z2, z4, z6, s5, Z2, and S5; forest litter in eastern Australia.............................. Asperolaelaps
   - Not as above.............................. 2

2. Sternal shieldsternal shield:
   a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
   with 3 cog-lkie circular ornaments; 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.
   short, club-shaped to spatulatespatulate:
   (Latin spatula = spoon) spatula-shaped; variously interpreted, but usually referring to setae that are flattened and somewhat expanded distally.
   ; 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 on bifid vertexvertex:
   an anterior extension of the idiosoma that covers the capitulum in many uropodid mites.
   .............................. Seritympanum
   - Not as above.............................. 3

3. Pretarsustarsal apotele:
   (also pretarsus) the most distal segments of legs and palps bearing the claws and empodium
   I without claws.............................. Ameroseiella
   - Pretarsustarsal apotele:
   (also pretarsus) the most distal segments of legs and palps bearing the claws and empodium
   I with claws.............................. 4

4. Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield with 24 or fewer 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.
   .............................. Epicriopsis
   - Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield with 27–29 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.
   .............................. 5

5. Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield with 27 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.
   ; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   II without ventral 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.
   .............................. Brontispalaelaps
   - Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield with 29 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.
   ; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   II with 2 ventral 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.
   .............................. 6

6. Anal shieldanal shield:
   in Mesostigmata, a ventral shield bearing the anal opening and circumanal setae (po, pa), but without any ventral setae or pores (lyrifissures) [see ventrianal shield]
   with 3 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.
   III with 1 pl 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.
   ; palp apotelepalptarsal apotele:
   (= palp apotele, palptarsal claw) the most distal segment of the palp; absent in Acariformes, claw-like in Opilioacarida, and a subdistal, tined structure in the Mesostigmata.
   3-tined.............................. Ameroseius
   - 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.
   with 5 or more 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.
   III with 2 pl 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.
   ; palp apotelepalptarsal apotele:
   (= palp apotele, palptarsal claw) the most distal segment of the palp; absent in Acariformes, claw-like in Opilioacarida, and a subdistal, tined structure in the Mesostigmata.
   2-tined.............................. Kleemannia

Ecology and distribution

Epicriopsis walteri Halliday lives in rainforest floor litter in Australia and can be reared on fungal hyphae. Other species are found in a variety of litter types and are assumed to be fungivores.

References

• Elsen and Whitaker 1985Elsen and Whitaker 1985:
  Elsen P and Whitaker JO, Jr. 1985. Seritympanum, a new genus of Ameroseiidae (Acarina, Mesostigmata) taken from rodents in the United States: including descriptions of three new species in the genus. Acarologia 26: 117-122.
• Evans 1963Evans 1963:
  Evans GO. 1963. The genus Neocypholaelaps Vitzthum (Acari: Mesostigmata). Annals and Magazine of Natural History (13th ser.) 6: 209-230.
• Halliday 1997aHalliday 1997a:
  Halliday RB. 1997a. Revision of the Australian Ameroseiidae (Acarina: Mesostigmata). Invertebrate Taxonomy 10: 179-201.
• Hughes 1976Hughes 1976:
  Hughes AM. 1976. The Mites of Stored Food and Houses (2nd ed.). Ministry of Agriculture, Fisheries and Food, Technical Bulletin 9. Her Majesty's Stationery Office, London.
• Seeman 1996Seeman 1996:
  Seeman OD. 1996. Flower mites and phoresy: The biology of Hattena panopla Domrow and Hattena cometis Domrow (Acari: Mesostigmata: Ameroseiidae). Australian Journal of Zoology 44: 193-203.
• Seeman and Walter 1995Seeman and Walter 1995:
  Seeman OD and Walter DE. 1995. Life history of Afrocypholaelaps africana (Evans) (Parasitiformes: Ameroseiidae), a mite inhabiting mangrove flowers and phoretic on honeybees. Journal of the Australian Entomological Society 34: 45-50.