Mesostigmata

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Taxonomy

updated 2025

Diagnostic characters

• Adult female usually with 2 subequal dorsal shields, rarely holodorsal or with fragmented opisthonotal shield
• Tibia I with 5 dorsal and 3 ventral setae
• Sternal shield with 3 pairs of setae, usually free from endopodal elements
• Palp apotele 3-tined

Key to common genera of Halolaelapidae

1. Adult female with holodorsal or divided dorsal shield; without posterior horn-like processes.............................. 2
   - Opisthonotal shield fragmented into mesonotal and pygidial elements; posterior of idiosoma with horn-like projections.............................. Saprosecans

2. Dorsal shield divided into 2 subequal shields............................... 3
   - Dorsal shield entire.............................. Halodarcia

3. Sternal shield subrectangular, without endopodal elements; peritreme not expanded posteriorly.............................. 4
   - Sternal shield angular, with fused endopodal elements; peritreme expanded posteriorly.............................. Leitneria

4. Genu III with 9 setae; coxa II without spine.............................. 5
   -   Genu III with 8 setae; coxa II with anterior spine.............................. Saprolaelaps

5. Genu IV with 9 setae; female with ventrianal shield.............................. Halolaelaps
   - Genu IV with 10 setae; female with anal shield.............................. Saintdidieria

Diagnosis

Pale to yellow or brown dermanyssine mesostigmatans mostly with subequal podonotal and opisthonotal shields, rarely holodorsal (Halodarcia) or with mesonotal and pygidial shields (Saprosecans). Peritremes short or long on narrow to broad shields. Sternal shield rectangular, without endopodal elements (except in Leitneria) bearing 3 pairs of setae (st1–3) and 2 pairs of lyrifissures (stp1–2); metasternal shields absent or present and bearing st4, stp3; genital shield usually trapezoidal to subrectangular and bearing 1 pair of setae; ventrianal shield broad, bearing 3–4 pairs of ventral setae or reduced to anal shield with 3 circumanal setae. Tarsus I with claws; trochanter I with 6 setae; tibia and genu I each with 5/3 dorsal/ ventral setae; genu IV with 9–10 setae, 5/1 dorsal/ ventral; coxae II sometimes with spine (Saprolaelaps). Chelicerae chelate-dentate; movable digit without excrescences. Palp genu with 6 setae, palp apotele 3-tined; corniculi horn-like. Tritosternum biflagellate with columnar base. Tectum with long median prong, evenly trifurcate, or denticulate. Female sperm induction pores at base of coxae IV. Males with genital opening at base of tritosternum in sternogenital shield; spermatodactyl usually simple.

Similar taxa

Halolaelapids are most likely to be confused with Ascidae, but have 3-tined palp apoteles. Also, ascids with 5 dorsal setae on tibia I usually have holodorsal or schizodorsal shields: halolaelapids typically have 2 subequal dorsal shields.

References

• Blaszak and Ehrnsberger 1999Blaszak and Ehrnsberger 1999:
  Blaszak C, Ehrnsberger R. 1999. A new species of the genus Halolaelaps Berlese & Trouessart, 1889 (Acari, Gamasida, Halolaelapidae) from the Spanish Mediterranean coast. Graellsia 55: 3–7.
• Evans and Fain 1995Evans and Fain 1995:
  Evans GO, Fain A. 1995. A new phoretic deuteronymph of Halodarcia Karg (Acari: Mesostigmata: Halolaelapidae) associated with carabid beetles in Belgium with a review of the genus. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique Entomologie 65: 63–71.
• Gwaiazdowicz 2001Gwaiazdowicz 2001:
  Gwiazdowicz DJ. 2001. Saprosecans bialoviensis sp. n. (Acari, Halolaelapidae) from Poland. Biologia (Bratislava) 56 (2): 149–153.
• Wisniewski et al. 1992Wisniewski et al. 1992:
  Wisniewski J, Karg W, Hirschmann W. 1992. Gangsystematik der Parasitiformes. Teil 547. Die Adultengattung Halozercon nov. gen., Typenart Halozercon karacholana nov. spec. aus Sibirien (Halolaelapidae, Ascoidea, Gamasina). Acarologie, Schriftenreihe für Vergleichende Milbenkunde 39: 180–186.