Venter (left) and dorsum of female Pediculaster americanus, from Walter et al. (2009).

Belongs within: Eleutherengonides.
Contains: Siteroptes, Acinogaster, Bakerdania, Pygmephorus, Imparipes, Scutacarus.

The Pygmephoroidea are a group of primarily free-living mites that mostly feed on fungi. Many species have dimorphic females with distinct phoretic and non-phoretic forms. This has lead to taxonomic confusion with different forms of a single species treated as distinct genera or even families. Members of the Siteroptidae have all setae on the first femur slender and are associated with plants or fungi. The Pygmephoridae have seta d on the first femur thickened and modified in shape, and are free-living or associated with fungi, insects or animal nests. Females of Siteroptidae and Pygmephoridae exhibit extreme hysterosomatic physogastry with offspring developing to or near maturity, and sometimes even mating, within the parent and often emerging when the mother's body wall ruptures (Walter et al. 2009). Certain species of the pygmephorid genus Pediculaster may infest commercial mushroom houses.

In members of the families Scutacaridae and Microdispidae, the prodorsum of females is usually covered to a greater or lesser extent by tergite C; these families may be separated as the Scutacaroidea. In Scutacaridae, tergite C of females forms a roof completely covering the prodorsum and gnathosoma; tergite C is less expansive in the Microdispidae. Males of Scutacaridae will locate immobile pharate female nymphs and carry them until they emerge as mature females, at which point they mate with them. Some Microdispidae appear to be parasitoids on insects, attaching themselves to the host by blade-like chelicerae or pedipalps (Walter et al. 2009).

See also: The Pygmephoroidea: lives of phoresy and fungi.

Characters (from Walter et al. 2009, as Pygmephoroidea + Scutacaroidea): Female gnathosoma capsulate, circular, oval or elongate, visible or hidden from above, with one or usually two pairs of dorsal setae; palpi closely appressed, usually reduced, rarely elongated and blade-lke; movable cheliceral digits stylet-like, partially retractile, rarely vestigial; pharynx divided into two or three muscular sections. Male gnathosoma reduced, tubiform, nonfunctional trophically. Prodorsal shield of females with pair of anterolateral stigmata (extended into troughlike peritremes in some taxa) and associated tracheae, and with two or usually three pairs of setiform setae and with or without a pair of anterolateral bothridia with capitate sensilla, the latter represented by a pair of normal scapular setae in larvae and males. Opisthosoma of females with first dorsal plate C entire, sometimes expanded anteriorly to overlap or cover prodorsum. Adults with coxisternal plates I-II united medially, forming prominent prosternal apodeme; female coxisternal plates III-IV united medially, usually forming poststernal apodeme. Female genital opening small, covered by consolidated aggenital plate, genital and aggenital setae usually absent (two pairs of aggenital setae present in Meristoplaxa). Males with plates C and D consolidated, and with aedeagus tubiform, enclosed in caudal genital capsule formed by consolidated plates H, PS, Ag. Females with legs I similar to or thicker than legs II-IV and with single claw sometimes enlarged for grasping, or thinner than other legs and without ambulacrum and claws; legs II-IV dissimilar in form, each with paired claws and stalked empodium or these absent on legs IV; trochanter IV quadrangular, longer than wide, in contrast to subtriangular trochanters I-III. Adult coxisternal plates I-II together with 4-6 pairs of setae; trochanters I-IV each with a setae; femur I with 3-5 setae; genu I with 2-4 setae; genu II with 2-3 setae. Male leg IV stout, its tarsus variably formed, with or without a single claw, with or without a broad, short empodium, sometimes with 1-2 apical setae elongated and 1-2 other apical setae short, spinelike. With two active postembryonic instars (larva and adult); single nymphal instar an inactive calyptostatic apoderm.

<==Pygmephoroidea [Scutacaroidea]
    |--Neopygmephorus Cross 1965 H98 [Neopygmephoridae ZF11]
    |    |--N. arvorum (Jacot 1936) SL71
    |    |--N. luxtoni Mahunka 1970 SL71
    |    |--N. novaezelandicus Mahunka 1970 SL71
    |    |--N. pannonicus (Willman 1951) SL71
    |    |--N. sellnicki (Krczal 1958) SL71
    |    |--N. tarsalis (Hirst 1921) SL71
    |    |--N. togatus (Willman 1942) SL71
    |    `--N. tripartitus Cross 1964 SL71
    |--Siteroptidae WL09
    |    |--Asensilla WL09
    |    |--Diroptes WL09
    |    |--Sevastianovella WL09
    |    |--Pseudobakerdania WL09
    |    |--Dudichiana WL09
    |    |--Metasiteroptes WL09
    |    |--Meristoplaxa [Meristoplaxinae] WL09
    |    |--Zambedania WL09
    |    `--Siteroptes H98
    |--Microdispidae [Microdispini] CT01
    |    |--Perperipes ornithocephala WL09
    |    |--Phyllodispus WL09
    |    |--Cochlodispus WL09
    |    |--Tubulodispus WL09
    |    |--Vietodispus WL09
    |    |--Scutodispus WL09
    |    |--Punicodoxa WL09
    |    |--Glyphidomastax WL09
    |    |--Myrmecodispus dorylini WL09
    |    |--Unguidispus WL09
    |    |--Caesarodispus WL09
    |    |--Reductodispus WL09
    |    |--Peponacara WL09
    |    |--Microdispus (Premicrodispus) WL09
    |    |    |--M. (P.) chandleri WL09
    |    |    `--M. (P.) lambi (Krczal 1964) WL09, H98 [=Pygmephorus lambi H98, Brennandania lambi H98]
    |    `--Brennandania Sasa 1961 H98
    |         |--B. angusta M83
    |         |--B. parasilvestris M83
    |         |--B. scolopendrae WL09
    |         `--B. silvestris M83
    |--Pygmephoridae [Pygmephorinae] C07
    |    |--Luciaphorus perniciosus [incl. L. auriculariae, L. hauseri] WL09
    |    |--Parapygmephorus costaricanus WL09, WP99
    |    |--Elattoma WL09
    |    |--Pediculitopsis tubiphorus WL09
    |    |--Petalomium fimbrisetum WL09, L86
    |    |--Xenaster longiabdominalis WL09
    |    |--Geotrupophorus WL09
    |    |--Spatulaphorus WL09
    |    |--Acarothorectes WL09
    |    |--Sasadania WL09
    |    |--Acinogaster RC79
    |    |--Sicilipes WL09
    |    |--Propygmephorus treati WL09
    |    |--Mahunkania WL09
    |    |--Pseudopygmephorus WL09
    |    |--Allopygmephorus WL09
    |    |--Siteroptoides trombidiphilus WL09
    |    |--Cerattoma WL09
    |    |--Rackia WL09
    |    |--Bakerdania WL09
    |    |--Microdispodides Vitzthum 1914 L86
    |    |--Termitacarus Trägårdh 1906 WL09, FH93
    |    |    `--T. ishiharai WL09
    |    |--Pygmephorus H98
    |    `--Pediculaster Vitzthum 1931 C07, H98
    |         |--P. americanus (Banks 1904) WL09, H98 [=Pigmephorus (l. c.) americanus H98, Pygmephorus americanus H98]
    |         |--P. australis C07
    |         |--P. flechtmanni WP99
    |         |--P. gautengensis C07
    |         |--P. gracilis C07
    |         |--P. mesembrinae (Canestrini 1881) [=Pygmephorus mesembrinae, Siteroptes mesembrinae] H98
    |         |--P. morelliae Rack 1975 C07, H98 [=Siteroptes morelliae H98]
    |         `--P. norrbomialis C07
    `--Scutacaridae [Disparipedidae] ZF11
         |--Archidispus WL09
         |--Lophodispus irregularis WL09
         |--Rettenmeyerella WL09
         |--Thaumatopelvis WL09
         |--Nasutiscutacarus WL09
         |--Parascutacarus indicus WL09, KK96
         |--Rhynchodispus WL09
         |--Lamnacarus Balogh & Mahunka 1963 BM63
         |    `--*L. ornatus Balogh & Mahunka 1963 BM63
         |--Imparipes WL09
         |--Scutacarus E91
         |--Disparipes Michael 1884 L86
         |--Heterodispus Paoli 1911 H98
         |    |--H. elongatus (Trägardh 1904) (see below for synonymy) M63
         |    |--H. horridus Mahunka 1967 H98
         |    `--H. longisetosus (Womersley 1955) [=Variatipes longisetosus] H98
         |--Pygmodispus Paoli 1911 H98
         |    `--P. (Allodispus) E91
         |         |--P. (A.) latisternus E91
         |         `--P. (A.) mancus Mahunka 1967 E91, H98
         |--Variatipes Paoli 1911 SB63
         |    |--*V. nudus (Berlese 1886) [=Disparipes nudus] SB63
         |    |--V. eucomus (Berlese 1908) [=Diversipes eucomus] SB63
         |    |--V. major Paoli 1911 SB63
         |    |--V. montanus Paoli 1911 SB63
         |    `--V. tridentinus Paoli 1911 SB63
         |--Diversipes Berlese 1903 H98
         |    |--*D. exhamulatus (Michael 1886) [=Disparipes exhamulatus] SB63
         |    |    |--D. e. exhamulatus SB63
         |    |    `--D. e. minor Schweizer 1951 SB63
         |    |--D. aequalis Mahunka 1967 H98
         |    |--D. dilatatus Bal. & Mah. 1962 M75
         |    |--D. horridolatus Mahunka 1975 H98
         |    |--D. pilosellus Mahunka 1967 H98
         |    `--D. setosus Mahunka 1967 H98
         `--Reductacarus Mahunka 1963 M63
              `--*R. singularis Mahunka 1963 M63

Heterodispus elongatus (Trägardh 1904) [=Imparipes elongatus; incl. I. (Heterodispus) elongatus var. capensis Paoli 1911] M63

*Type species of generic name indicated


[BM63] Balogh, J., & S. Mahunka. 1963. New scutacarids from Hungary (Acari: Tarsonemini). Acta Zoologica Academiae Scientiarum Hungaricae 9 (1–2): 61–66.

[C07] Camerik, A. M. 2007. Ecological studies on phoretic females of dung-inhabiting Pediculaster (Acari: Heterostigmata, Pygmephoridae) species in South Africa: emigration patterns from cow and horse dung. 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. 649–655. Instituto de Biología and Faculdad de Ciencias, Universidad Nacional Autónoma de México, Sociedad Latinoamericana de Acarología: México.

[CT01] Clift, A., & M. A. Terras. 2001. A quantitative study of phoresy in Microdispus lambi (Acari: Microdispidae) in eastern Australia. 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. 394–398. CSIRO Publishing: Melbourne.

[E91] Ebermann, E. 1991. Thanatosis or feigning death in mites of the family Scutacaridae. In: Schuster, R., & P. W. Murphy (eds) The Acari: Reproduction, development and life-history strategies pp. 399–401. Chapman & Hall: London.

[FH93] Farrier, M. H., & M. K. Hennessey. 1993. Soil-inhabiting and free-living Mesostigmata (Acari-Parasitiformes) from North America: an annotated checklist with bibliography and index. North Carolina Agricultural Research Service, North Carolina State University, Technical Bulletin 302: i–xvi, 1–408.

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

[KK96] Kumar, N. R., & R. Kumar. 1996. Mites in plant pollinator ecosystem: influence on conserving biodiversity. In: Mitchell, R., D. J. Horn, G. R. Needham & W. C. Welbourn (eds) Acarology IX vol. 1. Proceedings pp. 133–136. Ohio Biological Survey: Columbus (Ohio).

[L86] Lindquist, E. E. 1986. The world genera of Tarsonemidae (Acari: Heterostigmata): a morphological, phylogenetic, and systematic revision, with a reclassification of family-group taxa in the Heterostigmata. Memoirs of the Entomological Society of Canada 118 (S136): 1–517.

[M63] Mahunka, S. 1963. Beiträge zur Kenntnis der Milbenfauna (Acari) von Säugetiernestern. Acta Zoologica Academiae Scientiarum Hungaricae 9 (3–4): 355–372.

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

[RC79] Ross, L. J., & E. A. Cross. 1979. A revision of the genus Acinogaster (Acari: Pygmephoridae). International Journal of Acarology 5 (3): 231–250.

[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.

[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.

[WP99] Walter, D. E., & H. C. Proctor. 1999. Mites: Ecology, Evolution and Behaviour. CABI Publishing: Wallingford (UK).

[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.

Last updated: 18 June 2022.

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