Dorsum (left) and venter of Ereynetes meliponae, from OConnor & Klimov (2012).

Belongs within: Tydeoidea.
Contains: Pronematinae, Speleognathinae.

The Procurvata are a group of mites united by a procurved dehiscence line across the prodorsum, divided between the families Ereynetidae and Iolinidae (André & Fain 2000). Members of the Ereynetidae have two pairs of genital papillae, a characteristic deeply recessed solenidion in a sac-like structure on the first leg tarsus, and are often ornamented in a net-like pattern on the prodorsum and legs. They include the Lawrencacarinae, parasites in the nasal passages of anurans. Iolinidae have a single pair of genital papillae and usually have three or four elongated setae at the end of the tarsus. Within the Iolinidae, members of the subfamily Tydaeolinae lack an active tritonymphal instar (Walter et al. 2009).

Earth, arbor and airways
Published 26 August 2022

Some animal groups are notable for their bizarre morphologies, exhibiting kaleidoscopic arrays of ornamentation to bedazzle the eye. Others express their chaos in different ways, remaining calmly conservative in appearance but remarkably diverse in habits. The mites of the superfamily Tydeoidea definitely fall in the latter camp. Within this assemblage of small, fairly unremarkable-looking soft-bodied mites can be found microphages, predators and parasites, inhabiting locales from Arctic tundras to forest canopies to the nasal passages of vertebrates (Walter et al. 2009). The classification of tydeoids was overhauled by André & Fain (2000) who divided the superfamily between four families. Two of these, the Iolinidae and Ereynetidae, were also regarded as forming a clade that André & Fain dubbed the Procurvata.

Cartoon depictions of alternative dehiscence line patterns relative to position of setae ve in Tydeoidea, from André & Fain (2000); plesiomorphic condition on the left, condition in Procurvata on the right.

The name of the clade refers to the primary feature uniting its members, a procurved dehiscence line on the prodorsum. This is the line along which the cuticle splits when the mite is moulting. In other tydeoids (and I think in most mites), this breakage line forms a simple arc near the front of the dorsum. In Procurvata, it curves back in the middle. This difference in the dehiscence pattern is reflected in the distribution of setae on the prodorsum with median pairs shifted rearwards relative to lateral pairs.

The Iolinidae are the smaller of the two families of Procurvata with about 125 known species divided between the subfamilies Tydaeolinae, Pronematinae and Iolininae. These mites are united by a reduction in the size of the genital field (with only one or no pairs of genital papillae versus the two pairs found in other tydeoids). In at least the Pronematinae and Iolininae, this reduction is associated with the evolution of direct insemination instead of the more primitive mode of spermatophore deposition. Pronematinae and Iolininae are also characterised by the loss of terminal claws on the first pair of legs. These legs thus become more palp-like in appearance and may serve a sensory function.

Pronematus bonatii, from Berlese (1882).

Free-living iolinids may be found in soil or on vegetation. Many are omnivorous, feeding on honeydew, fungi, and other small invertebrates. One such species, the somewhat self-explanatorily named Pronematus ubiquitus, has been investigated as a predator of eriophyid gall mites. Other iolinids may be found as associates of insects, in nests or living on the insects themselves. The species Proctotydeus pyrohippeus has been found infesting the tympana of noctuid mites. The insect-associated Iolininae have the mobile cheliceral digit long and whip-like, presumably being used to feed on fluids from their host.

The Ereynetidae comprise about 180 known species, also divided between three subfamilies: the Ereynetinae, Lawrencacarinae and Speleognathinae. They are primarily characterised by the so-called ereynetal organ, a deeply recessed solenidion (a type of sensory hair) enclosed in a sclerotised pouch on the tibia of the first legs, connected to the surface by a fine canal and with a second, different type of hair alongside the canal opening. The function of this arrangement is currently unknown though it is presumably used to detect something. Suggestions include that it is somehow olfactory in purpose, or that it is used to detect moisture. The Ereynetinae are free-living, in soil or litter, or associated with other invertebrates. Members of the genus Riccardoella are found crawling on the skin or inside the mantle cavity of snails and slugs. Though they are blood-feeders, they are not generally thought to have much impact on their host except in extreme cases.

Riccardoella sp. on leopard slug Limax maximus, copyright Christophe Quintin.

Members of the subfamilies Lawrencacarinae and Speleognathinae are parasites living in the nasal passages of vertebrates: frogs and toads in the case of Lawrencacarinae, birds and mammals in the case of Speleognathinae. Lawrencacarines have a fairly typical development cycle for tydeoids (larva, three nymphal instars, adult) but speleognathines have been thought to moult directly from larva to adult without intervening nymphal stages. However, closer observation has demonstrated that speleognathines do indeed go through all three nymphal instars but none of them is active. Instead, the successive nymphal moults remain contained, matryoshka-style, within the original larval cuticle. Only when the mite reaches maturity does it emerge, ready to make its life within its gunky home.

Systematics of Procurvata
    |--Iolinidae [Iolinoidea]AF00
    |    |--PronematinaeWL09
    |    `--TydaeolinaeDW10
    |         |--Microtydeus Thor 1931WL09, A05
    |         |    `--M. beltraniM83
    |         `--TydaeolusWL09
    |              |--T. krantziM83
    |              |--T. loadmaniM83
    |              `--T. tenuiclavigerAF00
    `--Ereynetidae [Ereynetinae]AF00
         |  i. s.: Opsereynetes Thor 1932AF00
         |           `--O. simplexus Baker 1945AF00
         |         HanriccardoellaWL09
         |         Coccotydeus frequens Grandjean 1938G39, G38
         |         Aureliania Fain 1958H98
         |           `--A. aureliani (Fain 1955) [=Boydaia aureliani, Neoboydaia aureliani, N. aureliania (l. c.)]H98
         |         Domrownetes OConnor 1978H98
         |           `--D. exul (Domrow 1975) [=Paraspeleognathopsis exul]H98
         |         Neospeleognathopsis Fain 1958H98
         |           `--N. pteropus Fain & Lukoschus 1979H98
         |         Ophthalmognathus Dubinin 1957 [incl. Neospeleognathus Fain 1958]H98
         |         Paraspeleognathopsis Fain 1958H98
         |           |--P. bakeri (Fain 1955) [=Speleognathopsis bakeri]H98
         |           |--P. derricki (Womersley 1954) [=Boydaia derricki, Astrida derricki]H98
         |           `--P. exaeta Domrow 1991H98
         |         Psittaboydaia Fain 1985H98
         |           |--P. psittaculae (Fain 1962) [=Neoboydaia psittaculae]H98
         |           `--P. trichoglossi (Fain 1970) [=Aureliania trichoglossi]H98
         |         Ralliboydaia Fain 1962H98
         |           `--R. porphyrionis (Domrow 1965) [=Speleognathopsis porphyrionis]H98
         |         Ereynetoides watsoni Fain 1962SL71
         |--Gymnereynetes Fain 1964AF00, F76
         |    `--G. macquariensis (Fain 1962) [=Ereynetes (Gymnereynetes) macquariensis]F76
         |--Pseudotydeus [Pseudotydeinae]AF00
         |    `--P. perplexusAF00
         |--+--Huntereynetes Fain 1964AF00
         |  |    `--*H. scutulis (Hunter 1964) [=Ereynetoides scutulis, Ereynetes (*Huntereynetes) scutulis]AF00
         |  `--+--Hydranetes Kethley 1971AF00
         |     |    `--H. tropisternusAF00
         |     `--+--SpeleognathinaeAF00
         |        `--LawrencarinaeAF00
         |             |--Xenopacarus africanusAF00, WL09
         |             `--+--Batracarus hylaranaeAF00, AF91
         |                `--Lawrencarus Fain 1957AF00, H98
         |                     |--L. angelae (Womersley 1953) [=Boydaia angelae]H98
         |                     |--L. domrowi Fain 1961H98
         |                     |--L. eweriWL09
         |                     |--L. hylae Fain 1961H98
         |                     |    |--L. h. hylaeAF00
         |                     |    `--L. h. afrixaliAF00
         |                     `--L. lechriodiAF00
            |  `--Riccardoella Berlese 1923AF00
            |       |--*R. limacum (Schrank 1781) [=Acarus limacum]SB63
            |       |--R. concolorRP91
            |       `--R. oudemansi Thor 1932H98
            `--Ereynetes Berlese 1883AF00 [incl. Protereunetes Berlese 1923ZF11, SB63]
                 |  i. s.: E. berlesei Oudemans 1928SB63
                 |         *Protereunetes’ agilis Berlese 1923SB63
                 |         ‘Micrereunetes (Protereneutes)’ brevipes Berlese 1923SB63
                 |         E. exilisAF00
                 |         E. limacumS22
                 |         E. ministralis (Koch 1838) [=Tydeus ministralis]SB63
                 |         E. papuanusAF00
                 |--E. (Ereynetes)AF00
                 |    |--*E. (E.) polymitusAF00 (see below for synonymy)
                 |    |--E. (E.) fainiS76
                 |    |--E. (E.) galeatus (Berlese 1923) [=Micrereunetes galeatus]L90
                 |    |--E. (E.) husatoi Shiba 1976S76
                 |    `--E. (E.) tadakii Shiba 1976S76
                 `--E. (Anereynetes) meliponaeAF00

*Ereynetes (Ereynetes) polymitusAF00 [=Tydeus polymitusAF00; incl. T. celeripesCF77, T. melanchlaenusCF77, T. tetranemusCF77]

*Type species of generic name indicated


[A05] André, H. M. 2005. In search of the true Tydeus (Acari, Tydeidae). Journal of Natural History 39 (13): 975–1001.

[AF91] André, H. M., & A. Fain. 1991. Ontogeny in the Tydeoidea (Ereynetidae, Tydeidae and Iolinidae). In: Dusbábek, F., & V. Bukva (eds) Modern Acarology: Proceedings of the VIII International Congress of Acarology, held in České Budĕjovice, Czechoslovakia, 6–11 August 1990 vol. 2 pp. 297–300. SPB Academic Publishing: The Hague.

[AF00] André, H. M., & A. Fain. 2000. Phylogeny, ontogeny and adaptive radiation in the superfamily Tydeoidea (Acari: Actinedida), with a reappraisal of morphological characters. Zoological Journal of the Linnean Society 130: 405–448.

[CF77] Canestrini, G., & F. Fanzago. 1877. Intorno agli Acari Italiani. Atti del Reale Istituto Veneto di Scienze, Lettere ed Arti, Serie 5, 4: 69–208, pls 2–7.

[DW10] Dabert, M., W. Witalinski, A. Kazmierski, Z. Olszanowski & J. Dabert. 2010. Molecular phylogeny of acariform mites (Acari, Arachnida): strong conflict between phylogenetic signal and long-branch attraction artifacts. Molecular Phylogenetics and Evolution 56 (1): 222–241.

[F76] Fain, A. 1976. Acariens récoltés par le Dr. J. Travé aux iles subantarctiques II. Familles Acaridae, Anoetidae, Ereynetidae et Tarsonemidae (astigmates et prostigmates). Acarologia 18 (2): 302–328.

[G38] Grandjean, F. 1938. Observations sur les Tydeidae (2e série). Bulletin du Muséum d’Histoire Naturelle, 2e série 10 (6): 593–600.

[G39] Grandjean, F. 1939. Observations sur les acariens (5e série). Bulletin du Muséum National d’Histoire Naturelle, 2e Série 11 (4): 394–401.

[H98] Halliday, R. B. 1998. Mites of Australia: A checklist and bibliography. CSIRO Publishing: Collingwood.

[L90] Luxton, M. 1990. The marine littoral mites of the New Zealand region. Journal of the Royal Society of New Zealand 20 (4): 367–418.

[M83] Martin, N. A. 1983. Miscellaneous observations on a pasture fauna: an annotated species list. DSIR Entomology Division Report 3: 1–98.

[RP91] Raut, S. K., & A. Panigrahi. 1991. The mite Fuscuropoda marginata (C. L. Koch) for the control of pest slugs Laevicaulis alte (Férussac). In: Dusbábek, F., & V. Bukva (eds) Modern Acarology: Proceedings of the VIII International Congress of Acarology, held in České Budĕjovice, Czechoslovakia, 6–11 August 1990 vol. 2 pp. 683–687. SPB Academic Publishing: The Hague.

[S22] Schweizer, J. 1922. Beitrag zur Kenntnis der terrestrischen Milbenfauna der Schweiz. Verhandl. Naturf. Ges. Basel 33: 23–112, 4 pls.

[SB63] Schweizer, J., & C. Bader. 1963. Die Landmilben der Schweiz (Mittelland, Jura und Alpen): Trombidiformes Reuter, mit 217 Arten und Unterarten und 193 Originalzeichnungen. Denkschriften der Schweizerischen Naturforschenden Gesellschaft [Mémoires de la Société Helvétique des Sciences Naturelles] 84 (2): i–vi, 209–378.

[S76] Shiba, M. 1976. Taxonomic investigation on free-living Prostigmata from the Malay Peninsula. Nature and Life in Southeast Asia 7: 83–229.

[SL71] Spain, A. V., & M. Luxton. 1971. Catalog and bibliography of the Acari of the New Zealand subregion. Pacific Insects Monograph 25: 179–226.

[WL09] Walter, D. E., E. E. Lindquist, I. M. Smith, D. R. Cook & G. W. Krantz. 2009. Order Trombidiformes. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 233–420. Texas Tech University Press.

[ZF11] Zhang, Z.-Q., Q.-H. Fan, V. Pesic, H. Smit, A. V. Bochkov, A. A. Khaustov, A. Baker, A. Wohltmann, T. Wen, J. W. Amrine, P. Beron, J. Lin, G. Gabryś & R. Husband. 2011. Order Trombidiformes Reuter, 1909. In: Zhang, Z.-Q. (ed.) Animal biodiversity: an outline of higher-level classification and survey of taxonomic richness. Zootaxa 3148: 129–138.

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