Major mite taxa

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Taxonomy

updated 2025

Common names

sejines, sejids, uropodellids, ichthyostomatogasterids

Probability of encounter

low, most species are associated with treeholes, nests and other patchy habitats; most have deutonymphs that are phoretic on insects.

Quarantine importance

Low—as far as is known, all sejines are predators or scavengers.

Diagnosis

Mesostigmata with the female having a large genital shield usually bearing 6 to numerous setae, often bifurcate anteriorly, and covering the ovipore and an opening to a large, sac-like spermatheca; tarsus IV with well developed intercalary sclerite bearing setae av4/ pv4.

Body with moderate to extensive hypertrichy, numerous gland openings, and often densely tuberculate. Adult female dorsally with podonotal and pygidial shields (sometimes extensive) that may bear horns, and usually with mesonotal or mesolateral shields; secondary hardening of the cuticle often obscures the extent and number of these shields; with large ventrianal shield (sometimes developed dorso-laterally and fused to pygidial shield); usually large, free metapodal shields. Peritremes and peritrematal shields usually well developed, the latter fused anteriorly to podonotal shield and sometimes producing a process over the gnathosoma (vertex); lateral setae often on small platelets. Sternal area not fully sclerotised, but with seta-bearing platelets and often a shield bearing 2 pairs of setae. Males tend to have more consolidated body shields; the genital aperture is on an intercoxal shield and is covered by a subcircular valve. Phoretic deutonymphs have a cylindrical anal process and 1–2 dorsal shields. Tarsus I sometimes with an apicotarsus, with or without claws. Tarsus IV with 20 or more setae, including setae av4 and pv4 on a well defined intercalary sclerite. Tritosternum with well developed base and separate laciniae. Hypostomal seta h1 flattened, often scale-like; corniculi entire or bifid. Palp apotele 2-tined. Chelicerae chelate-dentate, slender with setiform pilus dentilis to massive without pilus dentilis; movable digit without arthrodial corona or excrescences.

Similar taxa

Some Monogynaspida (e.g., Ascidae) have posterior horns, but these species have entire sternal shields and never more than 2 setae on the female genital shield. Other monogynaspines (Microgyniina, some Uropodina, Heatherellina, and rare Dermayssina e.g., Halolaelapidae, Saprosecans) have fragmented dorsal shields, but all have sclerotised sternal regions, 0–1 pairs of setae on the female's genital shield, and lack setae av4/ pv4 and the intercalary sclerite of tarsus IV.

Ecology and distribution

The Sejidae is the most diverse family in the Sejida with ~30 described species of Sejus and 16 of Epicroseius, as well as numerous undescribed species in both genera. Sejids are common litter inhabitants in moist forests in the subtropics and tropics, especially in association with rotting wood, but are much less common in the Holarctic Region. Species of Sejus and Epicroseius are predatory on small arthropods and nematodes and have been collected from decaying fungi on logs; wood mulch in gardens; litter around logs in rainforests and wet sclerophyll; and suspended soils in the canopy. The chelicerae have small, serrate teeth and the anal opening is small. Only fluids of prey are ingested.  Males use their chelicerae to transfer a flask-shaped spermatophore to the anterior cleft of the female’s genital shield. One to four eggs are carried by gravid females. Deutonymphs of Sejina have been found as phoretics on beetles and flies and have a cylindrical extension of the anal opening that is used to attach to the carrier. Five species of Uropodella (Uropodellidae) have been described from the Americas and Africa, mostly associated with woody habitats. Species of Asternolaelaps (Ichthyostomatogasteridae), many undescribed, are known from Europe, North and South America, Australia and New Zealand. They have massive chelicerae and bifurcate corniculi that are used to bite-off and swallow pieces of fungi and small mites, and enlarged anal openings for eliminating solid wastes.

References

• Athias-Henriot 1972Athias-Henriot 1972:
  Athias-Henriot C. 1972. Gamasides Chiliens (Arachnides) II. Revision de la famille Ichthyostomatogasteridae Sellnick 1953 (=Uropodellidae Camin, 1955). Arquivos de Zoologia Sao Paulo 22: 113–191.
• Athias-Henriot 1977Athias-Henriot 1977:
  Athias-Henriot C. 1977. A new Australian mite, Archaeopodella scopulifera gen. et sp. n. (Gamasida: Liroaspidae). Journal of the Australian Entomological Society 16: 225–235.
• Camin 1955Camin 1955:
  Camin JH. 1955. Uropodellidae, a new family of mesostigmatid mites based on Uropodella lacinata Berlese, 1988 (Acarina, Liroaspina). Bulletin of the Chicago Academy of Sciences 10: 65–81.
• Domrow 1957Domrow 1957:
  Domrow R. 1957. Some Acarina Mesostigmata from the Great Barrier Reef. Proceedings of the Linnean Society of New South Wales 81: 197–216.
• Evans 1954Evans 1954:
  Evans GO. 1954. On the genus Asternolaelaps Berlese, 1923 (Acarina-Mesostigmata). Entomologists Monthly Magazine 90: 88–90.
• Gilyarov and Bregatova 1977Gilyarov and Bregatova 1977:
  Gilyarov MS, Bregatova NG, eds. 1977. Handbook for the identification of soil-inhabiting mites, Mesostigmata. Zoological Institute of the Academy of Sciences, Petrograd.
• Johnston 1982bJohnston 1982b:
  Johnston DE. 1982b. Mesostigmata. pp. 112–116. In: Parker SP, ed. Synopsis and classification of living organisms, Vol. 2. McGraw-Hill, New York.
• Kethley 1983bKethley 1983b:
  Kethley JB. 1983b. Modifications of the deutonymph of Uropodella lacinata Berlese, 1888, for phoretic dispersal (Acari: Parasitiformes). Journal of the Georgia Entomological Society 18: 151–155.
• Sellnick 1953Sellnick 1953:
  Sellnick M. 1953. Ichthyostomatogaster nyhleni, eine neue Acaride aus Schweden. Entomologisk Tidskrift 74: 24–37.
• Walter and Proctor 1998aWalter and Proctor 1998a:
  Walter DE, Proctor HC. 1998a. Feeding behaviour and phylogeny: Observations on early derivative Acari. Experimental and Applied Acarology 22: 39–50.
• Womersley 1959aWomersley 1959a:
  Womersley H. 1959a. A new Asternolaelaps from Australia (Acarina, Ichthyostomatogasteridae). Records of the South Australian Museum 13: 355–358.