Mesostigmata

t

Taxonomy

updated 2025

Diagnostic characters

• Tortoise-like uropodine mesostigmatans, usually oval to circular in outline and encased in armor dorsally and ventrally; shields usually indistinct, marginal and pygidial shields sometimes discernable.
• Usually >100 dorsal idiosomalidiosomal:
  (idiosomatic) adjectival form of idiosoma.
  setae
• Marginal setae sometimes elaborated to produce a fringe or basket-like arrangement
• Scabellumscabellum:
  in Uropodina, a platform-like structure on the underside of the vertex that receives the withdrawn legs I.
  and pedofossaepedofossa:
  (pl. pedofossae) (= fossae pedales, fovae pedales) recesses into which the legs can be withdrawn.
  usually present
• Peritremes often sinuous or bent; stigmata often at level of coxae II–III.
• Sternal setae (st1–5) on ventral shieldventral shield:
  in Mesostigmata, any shield or shields in the ventral region; often fused with the anal shield to form a ventrianal shield. [Back to Top]
  that encompasses the genital opening and protects all of the venterventer:
  the lower or under side; opposed to dorsum.
  ; anal opening with 2–5 circumanal setaecircumanal setae:
  in Mesostigmata, the three setae (postanal and pair of peranal) setae surrounding the anal opening.
  .
• Genital shieldgenital shield:
  a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
  nude, usually entirely intercoxal and truncate posteriorly (postcoxalpostcoxal:
  posterior to the coxae.  
  in Metagynella) often with anterior median process
• Legs I with or without ambulacra, coxae I large, flattened, usually contiguous; trochantertrochanter:
  the leg segment between the coxa and the femur.
  I with 4 setae; tibiatibia:
  (pl. tibiae) the leg segment between the genu and the tarsus.
  I with 3 dorsaldorsal:
  relating to the upper or back side; opposed to ventral.
  and 2 ventral setaeventral setae:
  in the Lindquist-Evans system used in the Mesostigmata, the ventral region has up to three longitudinal rows (Jv, Zv, Lv) with 1-5 transverse row designations.
  ; all genugenu:
  (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
  with <4 dorsaldorsal:
  relating to the upper or back side; opposed to ventral.
  setae; genugenu:
  (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
  II with <2 lateral setae.
• Chelicerae typically slender, elongate, with small digits and distaldistal:
  towards the free end of an appendage.
  sensory area (sometimes highly elaborated); 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.
  horn-like.
• 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.
  hyaline; hypostomal denticleshypostomal denticles:
  (teeth, retrorse teeth) the backwardly directed tooth-like projections on the elongate hypostome of ticks that are used to anchor the capitulum to skin while feeding.
  typically dense to irregular. Palp apoteleapotele:
  (Greek apotelein = to complete)—the terminus of an appendage; the most distal leg segment, often consisting of an empodium and a pair of claws. The apotele of a leg is usually treated as equivalent to the pretarsus or some part thereof (e.g., the claws and empodium), but the palptarsal apotele in Mesostigmata is a tined structure originating at the base of the palptarsus and thought to be a remnant of the claws. The chelicerae are also an appendage and terminate in the movable digit.
  2-tined; palppalp:
  (= pedipalp) the second pair of limbs in arachnids, used in feeding and originating on either side of the chelicerae.  In mites, the palps may be vestigial, with only a few segments, or have a maximum of  5 freely articulating segments (rarely the femur is subdivided) and a distal or subdistal apotele.
  genu with 4–5 setae, palppalp:
  (= pedipalp) the second pair of limbs in arachnids, used in feeding and originating on either side of the chelicerae.  In mites, the palps may be vestigial, with only a few segments, or have a maximum of  5 freely articulating segments (rarely the femur is subdivided) and a distal or subdistal apotele.
  femur with 5 (rarely 4) setae.
• Tritosternal laciniae typically fused, highly divided; tritosternal basetritosternal base:
  the usually columnar basal part of the tritosternum; sometimes expanded and rectangular or otherwise modified.
  variable, usually wider than long.
• Male genital opening usually intercoxal, anterior valve rarely with a pair of setae; chelicerae not obviously modified for sperm transfer.

Key to adult females of common Uropodoidea

1. Chelicerae with large, sclerotized node at basebase:
   the usually columnar basal part of the tritosternum; sometimes expanded and rectangular or otherwise modified; the most basal part of any structure.
   of movable digit.............................. 3
   - Chelicerae without large, sclerotized node.............................. 2

2. Genital opening intercoxal.............................. Uropodidae
   - Genital opening postcoxalpostcoxal:
   posterior to the coxae.  
   .............................. Metagynuridae, Metagynella

3. Fixed digitfixed digit:
   the distal extension of the middle article of the chelicera; usually bearing teeth and a distal hook and opposed to the movable digit in chelate-dentate forms, but often regressed; in Mesostigmata the fixed digit may bear the pilus dentilis.
   simple, lobed or acuminate distally, not ending in a flower-like process.............................. 4
   - Fixed digitfixed digit:
   the distal extension of the middle article of the chelicera; usually bearing teeth and a distal hook and opposed to the movable digit in chelate-dentate forms, but often regressed; in Mesostigmata the fixed digit may bear the pilus dentilis.
   ending in a flower-like process.............................. Uroactiniidae, Uroactinia

4. Pilus dentilispilus dentilis:
   (pl. pili dentilis) a seta-like or membranous sensory organ inserted ventrolaterally on the fixed digit of the chelicera of many Mesostigmata.
   absent or modified into a membranous process; internal malae linear.............................. 6
   - Pilus dentilispilus dentilis:
   (pl. pili dentilis) a seta-like or membranous sensory organ inserted ventrolaterally on the fixed digit of the chelicera of many Mesostigmata.
   bifurcate; internal malae densely plumose, moustache-likemoustache-like:
   having the appearance of a well developed handlebar moustache, as in the internal malae of most species of Veigaia (Mesostigmata).  
   .............................. Trachyuropodidae (5)

5. Bodybody:
   the idiosoma of mites.
   ornamented with large pits and/ or tubercles .............................. Trachyuropodidae, Trachyuropoda
   - Bodybody:
   the idiosoma of mites.
   flattened, oval, smooth to punctatepunctate:
   usually referring to ornamentation on shields resembling a dense array of needle punctures; with a granular appearance.
   , without large pits or tubercles.............................. Trachyuropodidae, Oplitis

6. Fixed digitfixed digit:
   the distal extension of the middle article of the chelicera; usually bearing teeth and a distal hook and opposed to the movable digit in chelate-dentate forms, but often regressed; in Mesostigmata the fixed digit may bear the pilus dentilis.
   produced as strong lobe or acuminate structure; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   I with pair of ventral setaeventral setae:
   in the Lindquist-Evans system used in the Mesostigmata, the ventral region has up to three longitudinal rows (Jv, Zv, Lv) with 1-5 transverse row designations.
   .............................. 9
   - Chelicerae chelate-dentatechelate-dentate:
   pincer-like chelicerae with teeth.
   , without distaldistal:
   towards the free end of an appendage.
   process; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   I without ventral setaeventral setae:
   in the Lindquist-Evans system used in the Mesostigmata, the ventral region has up to three longitudinal rows (Jv, Zv, Lv) with 1-5 transverse row designations.
   .............................. Trematuridae (7)

7. Peritremes present in adults (and deutonymphs).............................. 8
   - Peritremes absent in adults (present in deutonymphs) ..............................Trematuridae, Trematura

8. 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.
   denticulate, taperingtapering:
   drawn out or with margins converging.
   ; 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.
   divided; often with 1–2 pairs of elongate posteriorposterior:
   the back part of the body or towards that region in comparison, e.g., 'posterior to'.
   setae.............................. Trematuridae, Trichouropoda
   - 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.
   with distally branched process; 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.
   simple; without elongate distaldistal:
   towards the free end of an appendage.
   setae.............................. Trematuridae, Nenteria

9. Pedofossaepedofossa:
   (pl. pedofossae) (= fossae pedales, fovae pedales) recesses into which the legs can be withdrawn.
   usually present; internal malae simplesimple:
   unadorned; simple setae are needle-like and without hairs or pectins.
   or denticulatedenticulate:
   bearing small, sharp processes, e.g., the hypostome of ticks.
   .............................. 10
   - Pedofossaepedofossa:
   (pl. pedofossae) (= fossae pedales, fovae pedales) recesses into which the legs can be withdrawn.
   absent; internal malae bifurcatebifurcate:
   split into two distally or with two projections. 
   .............................. Dinychidae, Dinychus

10. Separate pygidial plate bearing setae present.............................. Urodiaspis
    - Pygidial region fused to dorsaldorsal:
    relating to the upper or back side; opposed to ventral.
    shield, sometimes produced as tooth-like process.............................. Uroobovella (11)

11. Metapodal lines and anterior genital shieldgenital shield:
    a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
    process absent.............................. Uroobovella (Uroobovella)
    - Metapodal lines present, anterior genital shieldgenital shield:
    a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
    process present or absent.............................. Uroobovella (Fuscouropoda)

Similar taxa

Well armored, tortoise-like mites with uropodine chelicerae are likely to be Uropodoidea.

Ecology and distribution

Uropodoids occur in most litter types and are especially common in compost and in mesic to wet forests. Some species infest worm beds, but probably have little effect on the worms. The few species that have been studied are primarily predatory (especially on maggots and nematodes), although some are known to feed on fungi as well. Insects, myriapods, and small lizards are often covered with the phoretic deutonymphs of these mites, each attached by a small anal pedicle.

References

• Ainscough 1981Ainscough 1981:
  Ainscough BD. 1981. Uropodine studies. I. Suprageneric classification in the cohort Uropodina Kramer, 1882 (Acari: Mesostigmata). International Journal of Acarology 7: 47–56.
• Athias 1976Athias 1976:
  Athias F. 1976. Observations morphologiques sur Polyaspis patavinus Berlese 1881 (Acariens: Uropodides). 2. Morphologie et chètotaxie des appendices au cours du dèveloppement postembryonnaire. Acarologia 18: 194–216.
• Athias-Binche and Bloszyk 1988Athias-Binche and Bloszyk 1988:
  Athias-Binche F, Bloszyk J. 1988. Australian Uropodina (Acari: Anactinotrichida). I. Australocilliba gen. n. (Cillibidae). Journal of the Australian Entomological Society 27: 1–8.
• Athias-Binche and Evans 1981Athias-Binche and Evans 1981:
  Athias-Binche F, Evans GO. 1981. Observations on the genus Protodinychus Evans, 1957 (Acari: Mesostigmata) with descriptions of the male and phoretic deuteronymph. Proceedings of the Royal Irish Academy (Section B) 81B: 25–36.
• Bloszyk and Halliday 1995Bloszyk and Halliday 1995:
  Bloszyk J, Halliday RB. 1995. A new species of Dinychus Kramer from Tasmania (Acarina: Dinychidae). Journal of the Australian Entomological Society 34: 187–191.
• Evans and Till 1979Evans and Till 1979:
  Evans EO and 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.
• Gilyarov and Bregatova 1977Gilyarov and Bregatova 1977:
  Gilyarov MS and Bregatova NG, eds. 1977. Handbook for the identification of soil-inhabiting mites, Mesostigmata. Zoological Institute of the Academy of Sciences, Petrograd.
• Johnston 1961Johnston 1961:
  Johnston DE. 1961. A review of the lower uropodid mites (former Thinozerconoidea, Protodinychoidea and Trachytoidea) with notes on the classification of the Uropodina (Acarina). Acarologia 3: 522-545.
• Karg 1989aKarg 1989a:
  Karg W. 1989a. Acari (Acarina), Milben Unterordnung Parasitiformes (Anactinotrichaeta) Uropodina Kramer, Schildkrötenmilben. Die Tierwelt Deutschlands 67: 1-203.
• Krantz and Ainscough 1990Krantz and Ainscough 1990:
  Krantz GW and Ainscough B. 1990. Mesostigmata. pp. 583-665. In: Dindal DL, ed. Soil biology guide. John Wiley & Sons, Brisbane.
• Wisniewski and Hirschmann 1993Wisniewski and Hirschmann 1993:
  Wisniewski J and Hirschmann W. 1993. Gangsystematik der Parasitiformes. Teil 548. Katalog der Ganggattungen, Untergattungen, Gruppen und Arten die Uropodiden der Erde. Acarologie, Schriftenreihe für Vergleichende Milbenkunde 40: 1-220.
• Womersley 1959bWomersley 1959b:
  Womersley H. 1959b. A new species of Urodiscella (Acarina, Uropodidae) from Australia. Records of the South Australian Museum 13: 349-353.