Mesostigmata

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Taxonomy

updated 2025

Diagnostic characters

• Female with holodorsal shield with setae of dorsal hexagon (j5, z5, j6) similar in form
• Genital shield +/- triangular, sharply tapering to a point and flanked by large metasternal shields
• Male with anterior genital aperture and distally fused spermatotreme on chelicerae
• Tibia I usually with 14 setae, including 4 ventral and 6 dorsal

Key to some Pergamasine genera (Adult females)

1. Holodorsal shield separate from ventral opisthogastric shield posteriorly.............................. 2
   - Dorsal shield fused to opisthogastric shield posteriorly.............................. Holoparasitus

2. Tarsus I with claws and pulvillus; holodorsal covering most of opisthosoma and bearing >20 pairs of setae.............................. 3
   - Tarsus I without claws and pulvillus; opisthonotal region of holodorsal shield reduced laterally and posteriorly and bearing <12 pairs of setae.............................. Pergamasellus

3. Opisthonotal region of holodorsal shield hypertrichous, with >30 pairs of setae.............................. 4
   - Opisthonotal region of holodorsal shield with <25 pairs of setae.............................. Paragamasus

4. Holodorsal and peritrematal shields completely fused.............................. Amblygamasus
   - Peritrematal shields cseparate from dorsal shield posteriorly.............................. Pergamasus

Diagnosis

Dorsal shield entire in both sexes and divided in deutonymphs. Peritrematal shield fully fused to dorsal shield. Female sternal shield with three pairs of setae; genital shield sharply triangular, flanked by large metasternal shields, and abutting or fused to a ventrianal shield that is variously fused with peritrematal and other shields. Tibia I typically with four ventral setae, six dorsal setae, and two al setae (2 3/2 3/2 2); tibia III with eight or nine setae (2 1/1 2/1 1(2)); chaetotaxy of genu IV (2 2/1 3/1 1). Palptarsal apotele 3-tined. Female often with an elaborate endogynium. Male with presternal genital aperture on holoventral or sternitigenital shield, and typically with highly developed spurs on legs II; chelicerae with sperm-holding structure (spermatotreme) which is coalesced distally with movable digit. Larva without pygidial shield; protonymphal pygidial shield reduced laterally, generally with 4–5 pairs of setae (without setae S4–S5), or shield sometimes absent.

Similar taxa

Similar taxa in key. Female Parasitinae have schizodorsal or divided dorsal shields with the dorsal hexagon setae dissimilar in form (usually z5 is larger and ornamented). Veigaiidae may be superficially similar, but have anal shields, a scale-like process above the palp apotele, often moustache-like internal malae, and a spermatodactyl that is free distally on the male chelicerae.

Similar taxa in key. Most members of the suborder Trigynaspida have three shields around the genital opening, but retain setae av4 and pv4 on an intercalary sclerite and excrescences on the movable digit. 

Ecology and distribution

Soil-inhabiting predators of small arthropods and other invertebrates. Most species appear to be bisexual and diplodiploidy has been demonstrated in the group. Phoresy is not known in the Pergamasinae.

References

• Bhattacharyya 1963Bhattacharyya 1963:
  Bhattacharyya SK. 1963. A revision of the British mites of the genus Pergamasus Berlese s.lat. (Acari: Mesostigmata). Bulletin of the British Museum (Natural History), Zoology 11 (2): 131–242 + 8 plates.
• Hennessey and Farrier 1989Hennessey and Farrier 1989:
  Hennessey MK, MH Farrier 1989. Mites of the family Parasitidae (Acari: Mesostigmata) inhabiting forest soils of North and South Carolina. NC Agricultural Research Service Technical Bulletin No. 291: 78 pp.
• Hyatt 1987Hyatt 1987:
  Hyatt KH. 1987. Mites of the genus Holoparasitus Oudemans, 1936 (Mesostigmata: Parasitidae) in the British Isles. Bulletin of the British Museum (Natural History) Zoology 52: 139–164.
• Juvara-Bals 2002Juvara-Bals 2002:
  Juvara-Bals I. 2002. A revision of the genus Heteroparasitus new status, with the description of Heteroparasitus (Medioparasitus) athiasae subgen. n., sp. n. from Spain and with a key to the genera of Pergamasinae (Acari, Gamasida, Parasitidae). Revue Suisse de Zoologie 109: 23–46.
• Micherdzinski 1969Micherdzinski 1969:
  Micherdzinski W. 1969. Die Familie Parasitidae Oudemans 1901 (Acarina, Mesostigmata). Zakład Zoologii Systematycznej Polskiej Akademii Nauk, Krakow. 690 pp.