The Eupodoidea are a group of mostly soft-bodied mites including predatory, fungivorous and phytophagous forms. They have freely articulating chelicerae, a famulus and at least one recumbent solenidion on tarsus I, and often a naso (Walter et al. 2009).
Members of the family Rhagidiidae produce silk that they use to protect themselves during moulting, and also in at least some cases in prey capture. They have strongly chelate chelicerae, and multiple solenidia on both the tibia and tarsus of the first pair of legs.
Smaller families of the Eupodoidea include Eriorhynchus, large (up to 1.8 mm) mites known only from Australia. They are conspicuously hairy with a hypertrichous naso, six or seven setae on the palptibia (three or fewer in other families) and more than fifteen setae on the subcapitulum (typically two or four in other families). Pilorhagidia and Pentapalpus unguempodius resemble Rhagidiidae in the possession of chelate chelicerae and are probably also predators. Pentapalpus unguempodius possesses palpi with five free segments, claw-like empodia, and two solenidia on tarsus I whereas Pilorhagidia and Rhagidiidae have palpi with four free segments, pad-like empodia, and three or more solenidia on tarsus I (Walter et al. 2009).
The Eupodoidea: earth mites and silk-weaving mites
Published 10 February 2014
I’d like, if I may, to introduce you to the Eupodoidea. These are a group of mites in the Prostigmata that can be found in soil or vegetation. Various species of eupodoids are predators or plant-eaters; as far as is known, the group doesn’t include members symbiotic with other animals. They are mostly soft-bodied (except for members of the family Penthalodidae) and generally small, though members of the Australian genus Eriorhynchus can grow to nearly two millimetres in length (yes, that’s big for a mite). Eupodoids are particularly diverse in cooler climates, though once again there are notable exceptions: the Hawaiian species Hawaiieupodes thermophilus inhabits volcanic steam vents with temperatures of up to 41°C (Walter et al. 2009). The first pair of legs are often used as sensory organs, being held in front of the body while the mite walks on the remaining three pairs.
The eupodoids are currently divided between nine families, some of which have only been established recently. The Cocceupodidae was establised by K. Jesionowska in 2010 for the genera Cocceupodes, Linopodes and Filieupodes, and the South African species Dendrodus acarus was described as its own family by P. A. S. Olivier in 2008 (unfortunately, he named this family the ‘Dendrochaetidae’, which is an invalid name because it was not based on an included genus). The genera Pilorhagidia (known from Hawaii and Europe) and Eriorhynchus are also placed in separate small families, as is the South African species Pentapalpus unguempodius. The habits of these various small families are little-known, but Pilorhagidia and Pentapalpus are probably predatory, and the large hairy Eriorhynchus may be herbivorous. Similarly uncertain in habits are the sclerotised mites of the Penthalodidae, whose two genera Penthalodes and Stereotydeus may be quite colourful and intricately ornamented.
The Penthaleidae is a family of plant-feeding mites that is most notorious for including some significant agricultural pests. These include the winter grain mite Penthaleus major and the red-legged earth mite Halotydeus destructor (it’s all in the name, really). Both these species feed on a range of crops. They both have dark central bodies with bright red legs, but the winter grain mite also has a reddish patch on its back marking the dorsal position of the anus (where the drop of liquid is being extruded in the photo above). Red-legged earth mites lack such a patch, and their anus is terminal in position.
The remaining two families are the most diverse. The Eupodidae often have the femora of the hind legs larger than the other legs, allowing them to rapidly jump backwards when threatened (such enlarged femora are also present in the Cocceupodidae). A number of Eupodes species feed on micro-algae. One eupodid, Benoinyssus najae was originally thought to be an animal symbiont as it was collected from the nasal fossae of a cobra. This species has since been found in soil and leaf litter, and it is thought that its original collection site was accidental.
The final family is the Rhagidiidae, a cosmopolitan group of carnivorous mites. Rhagidiids feed on other small arthropods, and are found in a wide range of habitats, including some that are restricted to caves. Members of the Rhagidiidae spin silk from glands near the chelicerae that they use for protection. Nymphs of Rhagidia species spin a web around themselves before they moult. In at least one species, Rhagidia longisensilla, the web is also used to capture prey: springtails that run into the web become entangled in it, and the mite is thus able to capture springtails twice its own size (Ehrnsberger 1979). I am not aware of any other animal outside spiders that use silk in this way, and I’d be interested if anyone else is.
Systematics of Eupodoidea
Characters (from Walter et al. 2009): Mostly soft-bodied, weakly sclerotised (except Penthalodidae), typically with one pair of prodorsal bothridial setae (setae vi may represent a second pair), with a pair of opisthonotal trichobothria also rarely present, one pair of lateral ocelli present (rarely absent); usually with an anteromedian naso (rarely absent), or with a naso-like epirostral projection bearing paired (rarely unpaired) ro setae. Opisthosoma typically with eight pairs of dorsal setae, rarely lacking setal pair f and one of the h series, or sometimes with postlarval neotrichy; cupules (lyrifissures) usually present, sometimes obscure, or absent. Ventrally with two (rarely three) pairs of genital papillae; anal opening ventral or terminal, occasionally dorsoterminal or dorsal; elements of opisthosomal segments PS and AD present, usually including two or three ps setae and sometimes ad1. Cheliceral bases separate and free from rostrum; with opposable cheliceral digits, or movable digits hook- or stylet-like and inserted subapically on remnant of fixed chela, fixed digit sometimes deformed, usually with one or two dorsal cheliceral setae (cha, chb; rarely absent). Palpi four- or rarely five-segmented, palptarsus with a typically recumbent anti-axial solenidion. Tarsi I–IV with claws, and each usually with setulose and pad-like, or rarely nude and claw-like, empodium. Tarsus I usually with one or more recumbent solenidia lying flush with tarsal surface in dorsal depressions, often with similar solenidia on tarsus II (rarely on tarsus III) and on tibiae I–II; solenidion of tibia II, when present, either completely recessed or inserted on surface. With five active postembryonic instars: larva, protonymph, deutonymph, tritonymph, and adult; a calyptostatic prelarva may be present.
<==Eupodoidea [Eupodinae] |--+--EupodidaeDW10 | `--PenthaleidaeDW10 `--RhagidiidaeDW10 |--FoveachelesZ01 | |--F. terricola (Koch 1835)Z01 | `--F. (Mediostella) willmanniNK94 |--EvadorhagidiaZ01 |--Troglocheles ginetiZ01, WL09 |--Arhagidia monothrixNK94 |--Shibaia heteropoda (Berlese 1910) (see below for synonymy)B96 |--Krantzia quadrisetaWL09 |--RobustochelesWL09 | |--R. hilli Strandtmann 1971E-VVM-M07 | `--R. mucronataWL09 |--TuberostomaWL09 | |--T. keithiWL09 | `--T. leechiWP99 |--CoccorhagidiaZ01 | |--C. clavifronsWL09 | |--C. pittardi Strandtmann 1971Z01 | `--C. subterranea (Berlese 1905) [=Rhagidia subterranea; incl. Brevipalpia minima Zacharda 1980]B96 |--PoecilophysisZ01 | |--P. (Dentocheles) pratensisNK94 | |--P. recussa (Thor 1909)Z01 | |--P. spelaea (Wankel 1861)Z01 | `--P. weyerensisWL09 |--HammeniaWHE88 |--RhagidiaS76 `--Lindquistula multisolenidiataNK94 Eupodoidea incertae sedis: Paraprotacarus hirsti Dubinin 1962AF00 Palaeotydeus devonicus Dubinin 1962AF00 Pilorhagidia Strandtmann & Goff 1977K90 [incl. Strandtmannia Zacharda 1978K90; StrandtmanniidaeZF11] |--P. celtarumWL09 `--P. hirsutaWL09 Eriorhynchus Qin & Halliday 1997H98 [EriorhynchidaeZF11] |--E. australicus (Womersley 1941) [=Penthalodes australicus]H98 |--E. hades Qin & Halliday 1997H98 |--E. ramosus Qin & Halliday 1997H98 |--E. walteri Qin & Halliday 1997H98 `--E. womersleyi Qin & Halliday 1997H98 PenthalodidaeZF11 PentapalpusWL09 [PentapalpidaeZF11] `--P. unguempodiusWL09 CocceupodidaeZF11 DendrochaetidaeZF11
Shibaia heteropoda (Berlese 1910) [=Rhagidia heteropoda; incl. R. longisensilla Shiba 1969, *Shibaia longisensilla]B96
*Type species of generic name indicated
[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.
[B96] Baker, A. S. 1996. On the status of some species of Eupodoidea (Acariformes: Prostigmata) represented in the Berlese Acaroteca. In: Mitchell, R., D. J. Horn, G. R. Needham & W. C. Welbourn (eds) Acarology IX vol. 1. Proceedings pp. 373–375. Ohio Biological Survey: Columbus (Ohio).
[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.
Ehrnsberger, R. 1979. Spinnvermögen bei Rhagidiidae (Acari, Prostigmata). Osnabrücker naturw. Mitt. 6: 45–72.
[E-VVM-M07] Estrada-Venegas, E. G., I. M. Vázquez & J. A. Moreno-Moreno. 2007. Prostigmatid mites (Acarida: Prostigmata) in decaying wood from “La Mancha” Veracruz, Mexico. 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. 691–695. Instituto de Biología and Faculdad de Ciencias, Universidad Nacional Autónoma de México, Sociedad Latinoamericana de Acarología: México.
[H98] Halliday, R. B. 1998. Mites of Australia: A checklist and bibliography. CSIRO Publishing: Collingwood.
Jesionowska, K. 2010. Cocceupodidae, a new family of eupodoid mites, with description of a new genus and two new species from Poland. Part I. (Acari: Prostigmata: Eupodoidea). Genus 21 (4): 637–658.
[K90] Kethley, J. 1990. Acarina: Prostigmata (Actinedida). In: Dindal, D. L. (ed.) Soil Biology Guide pp. 667–756. John Wiley & Sones: New York.
[NK94] Norton, R. A., & J. B. Kethley. 1994. Ecdysial cleavage lines of acariform mites (Arachnida, Acari). Zoologica Scripta 23 (3): 175–191.
Olivier, P. A. S. 2008. Dendrochaetidae, a new family of mites (Acari: Prostigmata), with descriptions of a new genus and species from South Africa. African Zoology 43 (1): 16–24.
[S76] Shiba, M. 1976. Taxonomic investigation on free-living Prostigmata from the Malay Peninsula. Nature and Life in Southeast Asia 7: 83–229.
[WHE88] Walter, D. E., H. W. Hunt & E. T. Elliott. 1988. Guilds or functional groups? An analysis of predatory arthropods from a shortgrass steppe soil. Pedobiologia 31: 247–260.
[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.
[WP99] Walter, D. E., & H. C. Proctor. 1999. Mites: Ecology, Evolution and Behaviour. CABI Publishing: Wallingford (UK).
[Z01] Zacharda, M. 2001. Talus formations—remarkable biotopes for acarological research, with examples from the Rhagidiidae (Acari: Prostigmata). 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. 269–271. CSIRO Publishing: Melbourne.
[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.