Mesostigmata

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Taxonomy

updated 2025

Diagnostic characters

• Yellow to brown dermanyssine mesostigmatans with holodorsal shields fully covering the dorsumdorsum:
  the upper or back side; opposed to venter.
  or taperingtapering:
  drawn out or with margins converging.
  to expose part of the lateral opisthosomaopisthosoma:
  (= abdomen) the posterior body division in arachnids; usually not distinct in mites because of the fusion of the opisthosoma with part of the prosoma to form the idiosoma.
  ; sometimes bearing unpaired setae in the J or Z rows
• Peritremes typically long; peritrematalperitrematal:
  (peritrematic) of or referring to the peritreme; adjectival form of peritreme.
  shields often narrow, rarely strongly produced. Sternal shield bearing 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.
  (st1–3) and 2 pairs of lyrifissures (stp1–2); metasternal shields usually absent st4, stp3 in soft cuticle (rarely st4 on small platelet or on endopodal-metasternal shield).
• Genital shieldgenital shield:
  a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
  usually tongue- to flask-shaped (opisthogastric) and bearing 1 pair (rarely 2–4 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.
  , rarely hologastric (Ololaelaps)
• 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]
  small, often inversely triangular to pear-shaped, bearing 3 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.
  
• Tarsustarsus:
  (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
  I with claws; trochantertrochanter:
  the leg segment between the coxa and the femur.
  I 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.
  ; tibiatibia:
  (pl. tibiae) the leg segment between the genu and the tarsus.
  and genugenu:
  (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
  I each with 6/3 dorsal/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.
  ; genugenu:
  (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
  IV with 9–10 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.
  , 5/2 dorsal/ventral; tarsustarsus:
  (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
  II sometimes with spines
• Chelicerae chelate-dentatechelate-dentate:
  pincer-like chelicerae with teeth.
  , 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.
  sometimes regressedregressed:
  reduce from normal as, for example, the capitulum of astigmatan deutonymphs or the fixed digit of the chelicerae in varroa.
  ; movable digit without excrescences
• 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 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.
  , 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- (rarely 3-) tined; 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- to bayonet-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.
  mucronate, denticulatedenticulate:
  bearing small, sharp processes, e.g., the hypostome of ticks.
  or smooth
• Subcapitular gutter usually with 6 denticulatedenticulate:
  bearing small, sharp processes, e.g., the hypostome of ticks.
  rows and a smooth anterioranterior:
  the front part of the body or towards that region in comparison, e.g., 'anterior to'
  line
• Female sperm induction pores 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 coxae IV
• Males with genital opening 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 tritosternumtritosternum:
  the sternum of the 3rd body segment (between legs I); produced as a biflagellate structure in Mesostigmata, although sometimes the flagellae (laciniae) are partially or completely fused.  
  in sternogenital shield; spermatodactylspermatodactyl:
  (also spermadactyl) the 'sperm finger' on the chelicerae of male dermanyssine Mesostigmata used to transfer sperm to the secondary sperm system in the female; spermatodactyls take various forms, from simple finger-like processes to very long, contorted structures.  
  typically simple

Similar taxa

Free-living soil mesostigmatans with a 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).
; an entire sternal shieldsternal shield:
a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
bearing 3 pairs of setae; a tongue-, axe head-, or flask-shaped genital shieldgenital shield:
a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
with 1 or more (rarely none) pairs of setae; and a small anal shield with 3 circumanal setaecircumanal setae:
in Mesostigmata, the three setae (postanal and pair of peranal) setae surrounding the anal opening.
are usually Laelapidae. Eviphidid, ameroseiids, and phytoseiidphytoseiid:
a member of the Phytoseiidae, including over 2000 described species, some of which are important biocontrol agents.  
mites may have similar anal shields, but typically have a posteriorly truncate genital shieldgenital shield:
a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
and a highly reduced leg and dorsaldorsal:
relating to the upper or back side; opposed to ventral.
shield chaetomechaetome:
a complement of setae; the setal array present on a stage or body part.
. Arctacarid mites are not known to occur in Australia but are superficially similar to laelapids. Arctacarids can be distinguished by their truncate dorsaldorsal:
relating to the upper or back side; opposed to ventral.
shield, 3-tined 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.
, and bifurcate 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.
. Ololaelaps species have a large opisthogenital shield and may be confused with some Parholaspididae or Ologamasidae; however, they lack an arthrodial brusharthrodial brush:
a brush like extension of the arthrodial membrane at the articulation of the movable and fixed digits in some Mesostigmata. Not to be confused with cheliceral excrescences that are produced from openings in the movable digit.
and have only 3 pairs of sternal setaesternal setae:
in Mesostigmata, the five pairs of setae in the intercoxal region designated st1-5; st1-3 are present in the larva and usually are borne on a sternal shield in the adult female; st4, the metasternal setae, are added in the deutonymph, often are borne on metasternal platelets, and sometimes on the sternal shield; st5, the genital setae, are added in the protonymph and usually borne on or are inserted laterad the epigynal shield in the adult female.
. Pseudoparasitus species have a flask-shaped opisthogenital shield that abuts an inversely triangular anal shield, similar to some Pachylaelapidae, but again have only 3 pairs of sternal setaesternal setae:
in Mesostigmata, the five pairs of setae in the intercoxal region designated st1-5; st1-3 are present in the larva and usually are borne on a sternal shield in the adult female; st4, the metasternal setae, are added in the deutonymph, often are borne on metasternal platelets, and sometimes on the sternal shield; st5, the genital setae, are added in the protonymph and usually borne on or are inserted laterad the epigynal shield in the adult female.
.

As well as the free-living soil mites that resemble free-living laelapids, a host of nest-, fur- and feather-inhabiting symbiotic Dermanyssoidea may be confused with Laelapidae. Whenever samples are from burrows, nests, tree hollows, soil near nests, carrion, or from other areas likely to contain parasites, a tentative identification of a laelapid mite should be checked against a key to parasitic Mesostigmata (e.g., Domrow 1988Domrow 1988:
Domrow R. 1988. Acari Mesostigmata parasitic on Australian vertebrates: An annotated checklist, keys and bibliography. Invertebrate Taxonomy 1: 817–948.) or taxa known to be associated with insects, spiders and myriapods.

Key to some common genera of soil-litter inhabiting Hypoaspidinae

1. Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield setae spatulatespatulate:
   (Latin spatula = spoon) spatula-shaped; variously interpreted, but usually referring to setae that are flattened and somewhat expanded distally.
   to spatulatespatulate:
   (Latin spatula = spoon) spatula-shaped; variously interpreted, but usually referring to setae that are flattened and somewhat expanded distally.
   -mucronate or paddle-shaped.............................. 2
   - Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield setae acuminate, not expanded distally .............................. 3

2. Digits of chelicerae and 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.
   elongate, the latter reaching 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.............................. Stratiolaelaps
   - Chelicerae and 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.
   not elongate .............................. Cosmolaelaps (pars)

3. With hologastric shieldhologastric shield:
   in Mesostigmata, a shield that covers the genital, ventral and anal regions; a ventrianal shield that incorporates the metapodal elements and is fused to the epigynal shield. 
   ; sternal shieldsternal shield:
   a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
   usually with 4 pairs of setae.............................. Ololaelaps
   - With genital or opisthogenital shields not fused to anal shield; 3 pairs of sternal shieldsternal shield:
   a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
   setae.............................. 4

4. With opisthogenital shield expanded to cover much of venterand abutting anal shield.............................. 5
   - With genital shieldgenital shield:
   a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
   , usually more or less tongue-shaped and separated from anal shield.............................. 6

5. All 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.
   captured by opisthogenital shield on margin; dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield setae often whip-likewhip-like:
   long, slender and sinuous as in the posterior setae of some phytoseiid mites (Mesostigmata) or the stylets of spider mites and their relatives (Prostigmata: Tetranychoidea).
   ; associated with ants.............................. Laelaspis
   - Usually 2 pairs 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.
   removed from margin of opisthogenital shield; dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield setae simplesimple:
   unadorned; simple setae are needle-like and without hairs or pectins.
   ; free-living, on wood with bark beetles, or rarely with ants............................... Pseudoparasitus

6. Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield setae scimitar-like or curved and taperingtapering:
   drawn out or with margins converging.
   from swollen basebase:
   the usually columnar basal part of the tritosternum; sometimes expanded and rectangular or otherwise modified; the most basal part of any structure.
   .............................. Cosmolaelaps (pars)
   - Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield setae simplesimple:
   unadorned; simple setae are needle-like and without hairs or pectins.
   .............................. 7

7. 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.
   elongate and inflated basally; genus IV with 9 setae.............................. Androlaelaps
   - 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.
   setiform, not inflated basally; genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   IV with 10 setae.............................. 8

8. 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.
   of chelicerachelicera:
   a limb on the presumed first body segment in chelicerate arthropods, the primary mouthparts.  In mites the chelicerae are primitively chelate-dentate, but may be modified into almost unrecognizable forms.  In Acariformes, the chelicerae are usually 2-segmented, but in other mites and some basal acariforms they have three segments.  Rarely, in some Uropodoidea (Mesostigmata), a subdivision makes them appear 4-segmented.
   with arched row of serrations; dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield taperingtapering:
   drawn out or with margins converging.
   posteriorly to expose much of opisthosomaopisthosoma:
   (= abdomen) the posterior body division in arachnids; usually not distinct in mites because of the fusion of the opisthosoma with part of the prosoma to form the idiosoma.
   , at least when female is well fed or gravid.............................. Gaeolaelaps
   - 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.
   without arched row of serrations; dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield usually broadly covering opisthsoma.............................. 9

9. Genital shieldgenital shield:
   a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
   expanded posteriorly, nearly reaching anal shield; setae JV1 on margin of shield or closely flanking shield.............................. "Hypoaspis" oblonga (Halbert) group
   - Genital shieldgenital shield:
   a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
   not expanded, well removed from anal shield; setae JV1 in soft cuticle.............................. "Hypoaspis" s.l.

Ecology and distribution

The Dermanyssoidea contains a diverse array of symbiotes (mostly parasites) of both insects and of vertebrates that have been variously distributed among about 17 different families. Free-living predators, however, occur in only one family, the Laelapidae. Unfortunately, this probable basalbasal:
towards the base of a structure; on a limb, towards the insertion on the body.
family in the Dermanyssoidea has the least clear taxonomic framework. Herein I follow the only recent analysis that has emphasized the free-living members of the Laelapidae, Casanueva (1993)Casanueva (1993):
Casanueva ME. 1993. Phylogenetic studies of the free-living arthropod associated Laelapidae (Acari: Mesostigmata). Gayana Zoologica 57: 21–46.. The Pseudoparasitini (including species of Hypoaspis in the broad sense) are mostly free-living general predators of arthropods and worms, but include some taxa that are closely associated with ant colonies (e.g., some Cosmolaelaps). After Uropodoidea and Ologamasidae, pseudoparasitines are often the most common and diverse mesostigmatans in Australian soils. Hypoaspidines include the vertebrate nest associated species of Androlaelaps, insect and spider associated Hypoaspis, and species of Coleolaelaps associated with scarabaeine beetles. Species of Laelaspis are ant associates.

References

• Casanueva 1993Casanueva 1993:
  Casanueva ME. 1993. Phylogenetic studies of the free-living arthropod associated Laelapidae (Acari: Mesostigmata). Gayana Zoologica 57: 21–46.
• Domrow 1957Domrow 1957:
  Domrow R. 1957. Some Acarina Mesostigmata from the Great Barrier Reef. Proceedings of the Linnean Society of New South Wales 81: 197-216.
• Domrow 1966aDomrow 1966a:
  Domrow R. 1966a. Some laelapid mites of syndactylous marsupials. Proceedings of the Linnean Society of New South Wales 90: 164-175.
• Domrow 1972Domrow 1972:
  Domrow R. 1972. Eight Australian species of Andreacarus Radford and Haemolaelaps Berlese (Acari: Dermanyssidae). Journal of the Australian Entomological Society 11: 105-113.
• Domrow 1988Domrow 1988:
  Domrow R. 1988. Acari Mesostigmata parasitic on Australian vertebrates: An annotated checklist, keys and bibliography. Invertebrate Taxonomy 1: 817-948.
• 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.
• Karg 1993Karg 1993:
  Karg W. 1993. Acari (Acarina), Milben Parasitiformes (Anactinochaeta) Cohors Gamasina Leach, Raubmilben. Die Tierwelt Deutschlands 59: 1-523.
• Krantz 1978Krantz 1978:
  Krantz GW. 1978. A manual of acarology [2nd ed.]. Oregon State University Book Stores, Corvallis.
• 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.
• Strong 1995Strong 1995:
  Strong KL. 1995. A new species of Hypoaspis (Acarina: Laelapidae) associated with funnel-web spiders (Araneae: Hexathelidae). In: Harvey MS, ed. Australasian spiders and their relatives: Papers honouring Barbara York Main. Records of the Western Australian Museum, Supplement 52: 219-223.
• Strong and Halliday 1994Strong and Halliday 1994:
  Strong KL and Halliday RB. 1994. Three new species of Hypoaspis Canestrini (Acarina: Laelapidae) associated with large Australian cockroaches. Journal of the Australian Entomological Society 33: 87-96.
• Walter 2003bWalter 2003b:
  Walter DE. 2003b. A new mite from an arboreal ant (Formicidae, Polyrachis sp.): Myrmozercon iainkayi sp. Nov. (Mesostigmata: Laelapidae). International Journal of Acarology 29 (1): 81-85.
• Walter and Oliver 1990Walter and Oliver 1990:
  Walter DE and Oliver JH, Jr. 1990. Geolaelaps oreithyiae, n. sp. (Acari: Laelapidae), a thelytokous predator of arthropods and nematodes, and a discussion of clonal reproduction in the Mesostigmata. Acarologia 30: 293-303.
• Walter et al. 2002Walter et al. 2002:
  Walter DE, Beard JJ, Walker K, and Sparks K. 2002. Of mites and bees: A review of mite-bee associations in Australia and a revision of Raymentia (Acari: Mesostigmata: Laelapidae), with the description of two new species of mites from Lasioglossum (Parasphecodes) spp. (Hymenoptera: Halictidae). Australian Journal of Entomology 41: 128-148.