Mesostigmata

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Taxonomy

updated 2025

Diagnostic characters

• Phytoseiidae with all 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.
  in the S-series and Z1 suppressed
• 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.
  s6 present, z3 absent; Z4–5 enlarged, barbed and with insertions contiguous.
• Genugenu:
  (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
  II with 7 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.
  ; genugenu:
  (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
  III with 6 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.
  .

Key to species of Platyseiella

1. 27 pairs of idiosomal 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.
   present, dorsal 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.
   J2 and R1 absent; r3 on dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield.............................. 2
   - 29 pairs of idiosomal 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.
   present, including J2 and R1; r3 in soft cuticle.............................. P. longicervicalis Moraes et al.

2. Peritremeperitreme:
   a groove or gutter on the surface connecting to a stigmatal opening.  In Mesostigmata the peritremes are lateral and run above the coxae of the legs and usually run to near the anterior margin of the idiosoma, but they may be very short or vestigial.  In Prostigmata peritremes are usually found on the anterior margin of the idiosoma, as short processes to either side of the capitulum (emergent peritremes), or as simple to complex lines or reticulations of short, connected chambers on the dorsal surface of the chelicerae or stylophore.
   extending to level 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.
   j1; Florida.............................. P. platypilis Chant
   - Peritremeperitreme:
   a groove or gutter on the surface connecting to a stigmatal opening.  In Mesostigmata the peritremes are lateral and run above the coxae of the legs and usually run to near the anterior margin of the idiosoma, but they may be very short or vestigial.  In Prostigmata peritremes are usually found on the anterior margin of the idiosoma, as short processes to either side of the capitulum (emergent peritremes), or as simple to complex lines or reticulations of short, connected chambers on the dorsal surface of the chelicerae or stylophore.
   shorter, extending only to level of j3; southern Africa.............................. P. marikae Ueckermann

Similar taxa

Species of Paraphytoseius (Amblyseiinae) strongly resemble Phytoseiinae but have serrateserrate:
with closely set teeth that resemble the cutting edge of a saw.
-chelate chelicerae and lack both setae z3 and s6. Species of Phytoseius have seta z3.

Key to genera of Phytoseiinae

1. Seta z3 absent, s6 present.............................. Platyseiella Muma
   - Seta z3 present, s6 present or absent............................... 2

2. Seta z6 absent, s6 present; dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield setae barbed, usually acicular, fine to thickened.............................. Phytoseius Ribaga
   - Seta z6 present, s6 absent; dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield setae spatulate/paddle-shaped.............................. Chantia Pritchard & BakerPritchard & Baker:
   A system of setal designations of spider mites in  Pritchard & Baker 1955 (A revision of the spider mite family Tetranychidae.  Mem. Pac. Coast Entomol. Soc. 2: 1-472.).  Dorsocentrals: D1 = c1; D2 = d1; D3 = e1; D4 = f1; D5 = h1; Dorsolaterals: L1 = c2; L2 = d2; L3 = e2; L4 = f2; Sublaterals: 1st sublaterals = c3; 2nd sublaterals = d3; 3rd sublaterals = e3; Humerals: H = c3;  also Inner sacrals (or DC4) = f1; Outer sacrals (or L4) = f2; Clunals (or DC5) = h1 or f3; Postanals (or posterior para-anals) = h2; Anterior para-anals = h3; Anals = ps1-3; 1st genitals (or anteromedial genitals) = g1; 2nd genitals (or posterolateral genitals)= g2;  Pregenitals = ag in the Grandjean system.
   

Ecology and distribution

One species of Platyseiella is know from each of three disparate regions: Thailand, Florida, and southern Africa.

References

• Beard and Walter 1996Beard and Walter 1996:
  Beard JJ, Walter DE. 1996. Australian mites of the genera Paraphytoseius and Paraamblyseius (Acarina: Phytoseiidae). Australian Journal of Entomology 35: 235–241.
• Chant and McMurtry 1994Chant and McMurtry 1994:
  Chant DA, McMurtry JA. 1994. A review of the subfamilies Phytoseiinae and Typhlodrominae (Acari: Phytoseiidae). International Journal of Acarology 20: 223–310.
• Moraes et al. 1989Moraes et al. 1989:
  Moraes GJ, Denmark HA, van den Berg H, and Bellotti A. 1989. Some phytoseiid mites (Acari: Phytoseiidae) from the Far East, with description of a new species. International Journal of Acarology 15: 129-133.
• Ueckerman 1990Ueckerman 1990:
  Ueckermann EA. 1990. A new species of the genus Platyseiella Muma, 1961 from South Africa (Acari: Phytoseiidae). International Journal of Acarology 16: 17-21.