Holothyrida (Holothyrina, Tetrastigmata)

Superorder Parasitiformes

  Order Holothyrida

     Families: Holothyridae, Allothyridae, Neothyridae

 

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 shield with short, broad peritremes above legs III and with or without one pair of lateral ocelli; the holoventral shield encompasses a posterior pair of anal valves each with ≥ 2 setae, and in the intercoxal region, a pair of transverse, setose genital valves in the male and usually 4 setose genital shields in the female.  Tritosternum present and flagelliform or absent; hypostome with ≥ 5 pairs of setae (including palpcoxal); sclerotized gnathotectum 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 & Distribution.  Holothyrans can be found in leaf litter, mosses, and under stones in moist forests from near sea level to about 2000 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, R.  1955.  A second species of Holothyrus (Acarina: Holothyroidea) from Australia.  Proc. Lin. Soc. N.S.W. 74: 159-162.

Johnston, D.E.  1982.  Acari.  In: Parker, S.P. (ed.)  Synopsis and classification of living organisms.  McGraw-Hill, New York, p. 111.

Krantz GW.  1978.  A Manual of Acarology.  OSU Bookstores: Corvallis.

Lee, D.C. and Southcott, R.V.  1979.  Spiders and other arachnids of South Australia.  Extract from South Australian Yearbook, 1979, D.J. Woolman, Government Printer, South Australia, 15 pp.

Lehtinen, P.T.  1981.  New Holothyrina (Arachnida, Anactinotrichida) from New Guinea and South America.  Acarologia 22: 3-13.

Lehtinen, P.T.  1991.  Phylogeny and zoogeography of the Holothyrida.  In: Dusabek, F. and Bukva, V. (eds.)  Modern Acarology, Volume 2.  SPB Academic Publishers, The Hague, pp. 101-113.

Lehtinen, P.T.  1995.  Revision of the Old World HOLOTHYRIDAE (Arachnida: Anactinotrichida: Holothyrina).  Invert. Taxon. 9: 767-826.

Pugh, P.J.A., Evans, G.O., Fordy, M.R., and King, P.E.  1991.  The functional morphology of the respiratory system of the Holothyrida (= Tetrastigmata) Acari: Anactinotrichida.  J. Zool. Lond. 225: 153-172.

Walter DE and Proctor HC.  1998.  Feeding behaviour and phylogeny: observations on early derivative Acari.  Experimental & Applied Acarology 22: 39-50.

Womersley, H.  1935.  A species of Acarina of the genus Holothyrus from Australia and New Zealand.  Ann. Mag. Nat. Hist. 16: 154-157.