Major mite taxa

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Taxonomy

updated 2025

Common names

holothyrans, holothyrids, allothyrids

Probability of encounter

very low

Quarantine importance

None. These mites are rare and of no known quarantine importance, although some species are toxic if ingested.

Diagnosis

Adults orange, red, reddish brown to almost black, beetle-like with fully sclerotized dome-shaped 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).
with short, broad peritremes above legs III and with or without one pair of lateral ocelliocellus:
(pl. ocelli) a simple eye.  Mites with eyes usually have one or two pairs of lateral ocelli, but some Opilioacarida have three pairs.  Additionally, some acariform mites have one or two median ocelli on the underside of the naso.
; the holoventral shield encompasses a posteriorposterior:
the back part of the body or towards that region in comparison, e.g., 'posterior to'.
pair of anal valves each with ≥2 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.
, and in the intercoxal region, a pair of transverse, setose genital valvesgenital valves:
sclerites covering the genital opening; usually referring to small sclerites (larger ones are usually called 'shields' or 'plates'.
in the male and usually 4 setose genital shields in the female. 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.  
present and flagelliform or absent; hypostome with ≥5 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.
(including palpcoxal); sclerotized 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.
absent. Chelicerae 3-segmented; palps 5-segmented; coxae free.

Similar taxa

Other relatively large and heavily sclerotised mites occur in the Brachypylina, Monogynaspida (especially the Ologamasidae), and Trigynaspida, but none of these will have the short, broad peritrematal plates, more than 5 pairs of subcapitular setae, or a dense covering of short setae.

Ecology and distribution

Holothyrans can be found in leaf litter, mosses, and under stones in moist forests from near sea level to about 2,000 m in elevation. Allothyrids and some holothyrids are known to scavenge, but none have been demonstrated to be predators. Field collections of Allothyrus in eastern Australia tend to have about equal numbers of adult males and females. Adults are lethargic animals that play dead when disturbed. Nymphs tend to be more active, and nymphal Allothyrus have a pair of large glands that open on the dorso-lateral aspects of the idiosoma that excrete fluid when the mites are annoyed. Adults of Holothyrus coccinella Gervais produce a distasteful exudate that is reported to be fatal to fowl that eat them.

References

• Domrow 1955Domrow 1955:
  Domrow R. 1955. A second species of Holothyrus (Acarina: Holothyroidea) from Australia. Proceedings of the Linnean Society of New South Wales 74: 159-162.
• Johnston 1982aJohnston 1982a:
  Johnston DE. 1982a. Acari. pp. 111. In: Parker SP, ed. Synopsis and classification of living organisms, Vol. 2. McGraw-Hill, New York.
• Krantz 1978Krantz 1978:
  Krantz GW. 1978. A manual of acarology [2nd ed.]. Oregon State University Book Stores, Corvallis.
• Lee and Southcott 1979Lee and Southcott 1979:
  Lee DC and Southcott RV. 1979. Spiders and other arachnids of South Australia: Extract from South Australian Yearbook, 1979. South Australian Museum. 15 pp.
• Lehtinen 1981Lehtinen 1981:
  Lehtinen PT. 1981. New Holothyrina (Arachnida, Anactinotrichida) from New Guinea and South America. Acarologia 22: 3-13.
• Lehtinen 1991Lehtinen 1991:
  Lehtinen PT. 1991. Phylogeny and zoogeography of the Holothyrida. pp. 101-113. In: Dusbabek F and Bukva V, eds. Modern Acarology, Vol. 2. Academia, Prague and SPB Academic Publishing, The Hague.
• Lehtinen 1995Lehtinen 1995:
  Lehtinen PT. 1995. Revision of the old world Holothyridae (Arachnida: Anactinotrichida: Holothyrina). Invertebrate Taxonomy 9: 767-826.
• Pugh et al. 1991Pugh et al. 1991:
  Pugh PJA, Evans GO, Fordy MR, and King PE. 1991. The functional morphology of the respiratory system of the Holothyrida (= Tetrastigmata) Acari: Anactinotrichida. Journal of Zoology (London) 225: 153-172.
• Walter and Proctor 1998aWalter and Proctor 1998a:
  Walter DE and Proctor HC. 1998a. Feeding behaviour and phylogeny: Observations on early derivative Acari. Experimental and Applied Acarology 22: 39-50.
• Womersley 1935Womersley 1935:
  Womersley H. 1935. A species of Acarina of the genus Holothyrus from Australia and New Zealand. Annals and Magazine of Natural History 16: 154-157.