Mesostigmata

t

Taxonomy

updated 2025

Diagnostic characters

• Female sternal shieldsternal shield:
  a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
  bearing 3 pairs of setaeseta:
  (pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
  (st4 on small metasternal shield or in soft cuticle)
• Genital shieldgenital shield:
  a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
  truncate posteriorly, with 1 pair of setaseta:
  (pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
  
• Ventrianal shieldventrianal shield:
  in Mesostigmata, a ventral shield bearing the anal opening, circum anal setae, and one or more pairs of ventral setae or pores (lyrifissures) [see anal shield]; maybe rather narrow or very broad and covering most of the gaster.
  narrow to subcordate and with 7–10 setaeseta:
  (pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
  
• Peritrematalperitrematal:
  (peritrematic) of or referring to the peritreme; adjectival form of peritreme.
  shield not extending beyond coxae IV

Similar taxa

Species of Zygoseius lack spurs on tarsitarsus:
(pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
II and have st4 on metasternal-endopodal plates. Species of Macrocheles have recurvedrecurved:
a curved suture or line of dehiscence that arches posteriorly; opposed to procurved.
peritremes.

Simplified key to common genera of Pachylaelapidae

1. Females (and usually males) with spurspur:
   a projection, usually tooth- or spine-like, from the body or limbs.
   -like distaldistal:
   towards the free end of an appendage.
   setae on tarsustarsus:
   (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
   II.............................. 3
   - Spurspur:
   a projection, usually tooth- or spine-like, from the body or limbs.
   -like setae on tarsustarsus:
   (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
   II absent.............................. 2

2. Female with subcordate ventrianal shieldventrianal shield:
   in Mesostigmata, a ventral shield bearing the anal opening, circum anal setae, and one or more pairs of ventral setae or pores (lyrifissures) [see anal shield]; maybe rather narrow or very broad and covering most of the gaster.
   with 13 setae (ZV1–2, JV1–3 + circumanals); genital shieldgenital shield:
   a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
   truncate posteriorly and bearing 1 pair of setae; sternal shieldsternal shield:
   a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
   with 3 pairs of setae and convex posteriorposterior:
   the back part of the body or towards that region in comparison, e.g., 'posterior to'.
   margin; metasternal setae on metasternal-endopodal shield; free-living or on dung beetles.............................. Zygoseius
   - Female with anal shield (rarely capturing 1–2 ventral setaeventral setae:
   in the Lindquist-Evans system used in the Mesostigmata, the ventral region has up to three longitudinal rows (Jv, Zv, Lv) with 1-5 transverse row designations.
   ); opisthogenital shield spreading laterally, with 2 pairs of setae and recurvedrecurved:
   a curved suture or line of dehiscence that arches posteriorly; opposed to procurved.
   posterior margin; associated with ants.............................. Sphaerolaelaps

3. Female sternal shieldsternal shield:
   a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
   bearing 4 pairs of setae, opisthogenital shield with 2 or more pairs of setae, and anal shield with 3 circumanal setaecircumanal setae:
   in Mesostigmata, the three setae (postanal and pair of peranal) setae surrounding the anal opening.
   .............................. 4
   - Female sternal shieldsternal shield:
   a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
   bearing 3 pairs of setae (st4 on small metasternal shield or in soft cuticle), genital shieldgenital shield:
   a shield or shields covering the genital opening; in female mongynaspine Mesostigmata this shield is usually called the epigynal (epigynial) shield.  
   with 1 pair of seta, and ventrianal shieldventrianal shield:
   in Mesostigmata, a ventral shield bearing the anal opening, circum anal setae, and one or more pairs of ventral setae or pores (lyrifissures) [see anal shield]; maybe rather narrow or very broad and covering most of the gaster.
   with 7–10 setae.............................. Pachyseius

4. Tibiatibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   I with 5 dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   setae; palp apotelepalptarsal apotele:
   (= palp apotele, palptarsal claw) the most distal segment of the palp; absent in Acariformes, claw-like in Opilioacarida, and a subdistal, tined structure in the Mesostigmata.
   3-tined.............................. 5
   - Tibiatibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   I with 6 dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   setae; palp apotelepalptarsal apotele:
   (= palp apotele, palptarsal claw) the most distal segment of the palp; absent in Acariformes, claw-like in Opilioacarida, and a subdistal, tined structure in the Mesostigmata.
   2-tined.............................. 6

5. Genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   I with 5 dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   setae.............................. Onchodellus
   - Genugenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   I with 6 dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   setae.............................. Pachylaelaps

6. Seta st4 on small metasternal plate; dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield with 37 pairs of setae.............................. Pachyseiulus
   - Seta st4 on in soft cuticle; dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield with 35 pairs of setae.............................. Pseudopachyseiulus

References

• Moraza 1993Moraza 1993:
  Moraza ML. 1993. Two new species of Pachyseius Berlese, 1910 from Spain (Acari, Mesostigmata: Pachylaelapidae). Acarologia 34: 89-94.
• Moraza and Johnston 1990Moraza and Johnston 1990:
  Moraza ML and Johnston DE. 1990. Pachyseiulus hispanicus n. gen., n. sp., from Navarre (northern Spain) (Acari: Mesostigmata: Pachylaelapidae). International Journal of Acarology 16: 213-218.
• Yin et al. 1986Yin et al. 1986:
  Yin S-G, Luc J, and Lian W-H. 1986. A new species and a new record of the genus Pachyseius from China (Acarina: Pachylaelapidae). Acta Zootaxonomica Sinica 11 (2): 191-193.