Oribotritia sp., copyright Tom Murray.

Belongs within: Ptyctima.

Oribotritia is a cosmopolitan genus of euphthiracaroid box mites (Subías 2004).

Oribotritia: some mites just want to be left alone
Published 10 December 2013

I’m aware that a lot of people would not automatically think of mites when categorising cuteness, but I dare you to look at the animal in the photo above (taken by Tom Murray) and tell me it’s not adorable. This is a box mite of the genus Oribotritia, a cosmopolitan genus found on all the continents except Australia. More than 80 species of Oribotritia have been described so far, and there’s probably more to come. Box mites are armoured mites with a body form known as ‘ptychoid’; this means that the legs can be drawn back close to the body, and the prodorsum (the articulated shield at the front of the body covering the mouthparts) folded over to cover the soft parts. The figure below from Schmelzle et al. (2009) shows how it works. The mite on the left is Oribotritia banksi, the one on the right is a different ptychoid, Rhysotritia ardua:

This figure also shows some of the distinguishing features of Oribotritia. There are a number of families of ptychoid mites; interestingly, indications are that not all ptychoids are directly related to each other. Instead, the ptychoid morphology has evolved a number of times. Oribotritia belongs to the ‘true’ box mites, in which the notogaster (the main ‘body’ of the mite) is a single undivided dorsal plate, while the genital and anal plates are long and together occupy the entire length of the underside. The three main families of true box mites are the Phthiracaridae, Oribotritiidae and Euphthiracaridae. Phthiracarids have the ventral plates broad and the venter overall more or less U-shaped; the other two families have the venter narrow and triangular. In oribotritiids like Oribotritia, the genital and anal plates have another elongate pair of plates running outside them, but in euphthiracarids (like Rhysotritia ardua in the figure above), all the ventral plates have become fused into a single plate pair.

When fully withdrawn into its sclerotised shell, the ptychoid mite is pretty effectively sealed away from would-be predators. As well as this mechanical defense, glandular openings on the side of the notogaster secrete defensive oils to repel predators chemically. The overall aim is that the mite should simply be left unmolested to pursue its own interests: feeding on decaying vegetation.

Systematics of Oribotritia

Characters (from Balogh & Balogh 1992, as Oribotritia + Berndotritia): Bothridial squama situated above bothridium. Posterior median apodeme present. Genital-aggenital suture complete, genital and aggenital plates well separated; genital setae in paraxial position, in longitudinal row; ano-genital cleft oblique, well developed; interlocking triangle absent.

<==Oribotritia Jacot 1924 (see below for synonymy)S04
    |--O. berlesei (Michael 1898)S04 (see below for synonymy)
    |--O. africana Starý 1993 [incl. O. bicarinata Niedbała 1993]S04
    |--O. ampla Niedbała 1991S04
    |--O. anceps Niedbała 2000S04
    |--O. angusta Mahunka 1982S04
    |--O. aokii Mahunka 1987S04
    |--O. asiatica Hammer 1977 [incl. O. koreense Mahunka 1982]S04
    |    |--O. a. asiaticaS04
    |    `--O. a. norikoae Suzuoka 1983S04
    |--O. attenuata Niedbała & Schatz 1996S04
    |--O. bagnalli (Hull 1916) [=Phthiracarus bagnalli]S04
    |--O. banksi (Oudemans 1916) [=Tritia banksi]S04
    |--O. bipartita Niedbała 2000S04
    |--O. brevis Niedbała & Colloff 1997S04
    |--O. brevisetosa Niedbała 2003N07
    |--O. bulbifer (Mahunka 1987)S04 [=*Berndotritia bulbiferBB92]
    |--O. capitanea Niedbała & Corpuz-Raros 1998S04
    |--O. carolinae Jacot 1930S04
    |--O. cherokee Niedbała 2002S04
    |--O. chichijimensis Aoki 1980 [incl. O. chichijimensis ryukyuensis Nakatamari 1985]S04
    |--O. contortula Niedbała 1993S04
    |--O. contraria Niedbała 1993N06
    |--O. corporaali (Oudemans 1926) [=Tritia corporaali]S04
    |--O. decumana (Koch 1836) (n. d.) [=Hoplophora decumana]S04
    |--O. didyma Niedbała & Schatz 1996S04
    |--O. duplex Niedbała 2000S04
    |--O. exilis (Sellnick 1923) [=Tritia exilis]S04
    |--O. faroensis Selln. 1930T31
    |--O. fennica Forsslund & Märkel 1963S04
    |--O. gigas Bayoumi & Mahunka 1979S04
    |--O. hauseri Mahunka 1982S04
    |--O. hawaiiensis (Jacot 1929) [=Euphthiracarus (Indotritia) hawaiiensis]S04
    |--O. henicos Niedbała 2002S04
    |--O. hermanni Grandjean 1967S04
    |--O. heterotricha Niedbała 2000S04
    |--O. incognita Niedbała 2000S04
    |--O. laselve Niedbała 2003N07
    |--O. magna (Ewing 1907) [=Phthiracarus magnus]S04
    |--O. megale (Walker 1965) [=Plesiotritia megale]S04
    |--O. nepalensis Niedbała 2000S04
    |--O. nudaG33b
    |--O. opipara Niedbała 2002S04
    |--O. oregonensis Niedbała 2002S04
    |--O. paraaokii Niedbała 2000S04
    |--O. paraincognita Niedbała 2006N06
    |--O. paraspinosa Mahunka 1999S04
    |--O. pulla Niedbała 1998S04
    |--O. pyropus (Sellnick 1918)S93
    |--O. rafalskii Niedbała 1997S04
    |--O. samoaensis Niedbała 1998S04
    |--O. serrata Feider & Suciu 1958S04
    |--O. serrula Niedbała & Schatz 1996S04
    |--O. solitaria Niedbała 1993S04
    |--O. spinosa (Mahunka 1988) [=Philotritia spinosa]S04
    |--O. storkani Feider & Suciu 1957S04
    |--O. submolesta Niedbała 2000S04
    |--O. subsolanaN01
    |--O. succincta Niedbała 1998S04
    |--O. teretis Niedbała 1993S04
    |--O. tiwi Mahunka 1987S04
    |--O. tokukoae Aoki 1973S04
    |--O. translucida Sellnick 1931S93
    |--O. trisetosa Niedbała & Schatz 1996S04
    `--O. virgulata Niedbała 2001S04

Oribotritia Jacot 1924 [incl. Berndotritia Mahunka 1987, Philotritia Mahunka 1988, Plesiotritia Walker 1965, Tritia Berlese 1883 (preoc.)]S04

Oribotritia berlesei (Michael 1898)S04 [=Phthiracarus berleseiS04, Hoplophora decumana Berlese 1883 non Koch 1836S04, *Oribotritia decumanaS04, Tritia decumanaG33a]

*Type species of generic name indicated


[BB92] Balogh, J., & P. Balogh. 1992. The Oribatid Mites Genera of the World vol. 1. Hungarian Natural History Museum: Budapest.

[G33a] Grandjean, F. 1933a. Structure de la région ventrale chez quelques Ptyctima (oribates). Bulletin du Muséum, 2e série, 5 (4): 309–315.

[G33b] Grandjean, F. 1933b. Observations sur les oribates (5e série). Bulletin du Muséum, 2e série, 5 (6): 461–468.

[N01] Niedbała, W. 2001. Study of the diversity of Ptyctima (Acari: Oribatida) and quest for centres of its origin: the fauna of the Oriental and Australian regions. In: Halliday, R. B., D. E. Walter, H. C. Proctor, R. A. Norton & M. J. Colloff (eds) Acarology: Proceedings of the 10th International Congress pp. 143–148. CSIRO Publishing: Melbourne.

[N06] Niedbała, W. 2006. Supplement to the knowledge of ptyctimous mites (Acari: Oribatida) from Australian region. Annales Zoologici 56 (Suppl. 1): 99–156.

[N07] Niedbała, W. 2007. Ptyctimous mites (Acari, Oribatida) of Costa Rica. In: Morales-Malacara, J. B., V. M. Behan-Pelletier, E. Ueckermann, T. M. Pérez, E. G. Estrada-Venegas & M. Badii (eds) Acarology XI: Proceedings of the International Congress pp. 39–42. Instituto de Biología and Faculdad de Ciencias, Universidad Nacional Autónoma de México, Sociedad Latinoamericana de Acarología: México.

Schmelzle, S., L. Helfen, R. A. Norton & M. Heethoff. 2009. The ptychoid defensive mechanism in Euphthiracaroidea (Acari: Oribatida): a comparison of muscular elements with functional considerations. Arthropod Structure and Development 38: 461–472.

[S93] Selden, P. A. 1993. Arthropoda (Aglaspidida, Pycnogonida and Chelicerata). In: Benton, M. J. (ed.) The Fossil Record 2 pp. 297–320. Chapman & Hall: London.

[S04] Subías, L. S. 2004. Listado sistemático, sinonímico y biogeográfico de los ácaros oribátidos (Acariformes, Oribatida) del mundo (1758–2002). Graellsia 60 (número extraordinario): 3–305.

[T31] Trägårdh, I. 1931. Acarina from the Juan Fernandez Islands. Natural History of Juan Fernandez and Easter Islands 3 (4): 553–628.

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