Mesostigmata

t

Taxonomy

updated 2025

Diagnostic characters

• Yellow to brown dermanyssine mesostigmatans with holodorsal shields fully covering the dorsum or tapering to expose part of the lateral opisthosoma; sometimes bearing unpaired setae in the J or Z rows
• Peritremes typically long; peritrematal shields often narrow, rarely strongly produced. Sternal shield bearing 3 pairs of setae (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 shield usually tongue- to flask-shaped (opisthogastric) and bearing 1 pair (rarely 2–4 or more pairs) of setae, rarely hologastric (Ololaelaps)
• Anal shield small, often inversely triangular to pear-shaped, bearing 3 circumanal setae
• Tarsus I with claws; trochanter I with 6 setae; tibia and genu I each with 6/3 dorsal/ventral setae; genu IV with 9–10 setae, 5/2 dorsal/ventral; tarsus II sometimes with spines
• Chelicerae chelate-dentate, fixed digit sometimes regressed; movable digit without excrescences
• Palp genu with 6 setae, palp apotele 2- (rarely 3-) tined; corniculi horn- to bayonet-like
• Tectum mucronate, denticulate or smooth
• Subcapitular gutter usually with 6 denticulate rows and a smooth anterior line
• Female sperm induction pores at base of coxae IV
• Males with genital opening at base of tritosternum in sternogenital shield; spermatodactyl typically simple

Similar taxa

Free-living soil mesostigmatans with a holodorsal shield; an entire sternal shield bearing 3 pairs of setae; a tongue-, axe head-, or flask-shaped genital shield with 1 or more (rarely none) pairs of setae; and a small anal shield with 3 circumanal setae are usually Laelapidae. Eviphidid, ameroseiids, and phytoseiid mites may have similar anal shields, but typically have a posteriorly truncate genital shield and a highly reduced leg and dorsal shield chaetome. Arctacarid mites are not known to occur in Australia but are superficially similar to laelapids. Arctacarids can be distinguished by their truncate dorsal shield, 3-tined palp apotele, and bifurcate pilus dentilis. Ololaelaps species have a large opisthogenital shield and may be confused with some Parholaspididae or Ologamasidae; however, they lack an arthrodial brush and have only 3 pairs of sternal setae. 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 setae.

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. Dorsal shield setae spatulate to spatulate-mucronate or paddle-shaped.............................. 2
   - Dorsal shield setae acuminate, not expanded distally .............................. 3

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

3. With hologastric shield; sternal shield usually with 4 pairs of setae.............................. Ololaelaps
   - With genital or opisthogenital shields not fused to anal shield; 3 pairs of sternal shield setae.............................. 4

4. With opisthogenital shield expanded to cover much of venterand abutting anal shield.............................. 5
   - With genital shield, usually more or less tongue-shaped and separated from anal shield.............................. 6

5. All ventral setae captured by opisthogenital shield on margin; dorsal shield setae often whip-like; associated with ants.............................. Laelaspis
   - Usually 2 pairs of ventral setae removed from margin of opisthogenital shield; dorsal shield setae simple; free-living, on wood with bark beetles, or rarely with ants............................... Pseudoparasitus

6. Dorsal shield setae scimitar-like or curved and tapering from swollen base.............................. Cosmolaelaps (pars)
   - Dorsal shield setae simple .............................. 7

7. Pilus dentilis elongate and inflated basally; genus IV with 9 setae.............................. Androlaelaps
   - Pilus dentilis setiform, not inflated basally; genu IV with 10 setae.............................. 8

8. Fixed digit of chelicera with arched row of serrations; dorsal shield tapering posteriorly to expose much of opisthosoma, at least when female is well fed or gravid.............................. Gaeolaelaps
   - Fixed digit without arched row of serrations; dorsal shield usually broadly covering opisthsoma.............................. 9

9. Genital shield expanded posteriorly, nearly reaching anal shield; setae JV1 on margin of shield or closely flanking shield.............................. "Hypoaspis" oblonga (Halbert) group
   - Genital 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 basal 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, 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, 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, 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, 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, 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, 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.