Mesostigmata

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Taxonomy

updated 2025

Diagnostic characters

• Melicharinae with dorsaldorsal:
  relating to the upper or back side; opposed to ventral.
  shield deeply incised (i.e., schizodorsal) and lacking 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.
  z3
• Movable digit with 0–1 tooth

Similar taxa

Similar taxa not in the Lucid key (see below). Orolaelaps De Leon, Mycolaelaps Lindquist

Key to the genera of Melicharinae

1. Idiosoma narrow, dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield greater than twice as long as wide; leg setation strongly neotenous, genuagenu:
   (pl. genua) (= patella) the 4th leg segment, between the femur and tibia.
   I–II–III–IV with 12–7–6–7 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.
   , tibiaetibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   with 11–7–6–6 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.
   ; female lacking metasternal plates and with ventri-anal shieldanal shield:
   in Mesostigmata, a ventral shield bearing the anal opening and circumanal setae (po, pa), but without any ventral setae or pores (lyrifissures) [see ventrianal shield]
   bearing 1–3 pairs of ventral 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 addition to circumanal 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.
   .............................. Mycolaelaps
   - Idiosoma broader, legs not strongly neotenous, metasternal plates present or absent, only anal shieldanal shield:
   in Mesostigmata, a ventral shield bearing the anal opening and circumanal setae (po, pa), but without any ventral setae or pores (lyrifissures) [see ventrianal shield]
   or separate anal and ventralventral:
   relating to the lower or under side; opposed to dorsal.
   shields.............................. 2

2. Female with separate ventral shieldventral shield:
   in Mesostigmata, any shield or shields in the ventral region; often fused with the anal shield to form a ventrianal shield. [Back to Top]
   bearing 4 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.
   between genital and anal shields; posteriorposterior:
   the back part of the body or towards that region in comparison, e.g., 'posterior to'.
   connection of peritrematalperitrematal:
   (peritrematic) of or referring to the peritreme; adjectival form of peritreme.
   shield to exopodal plate beside coxacoxa:
   the basal segment of the leg, articulating with (Parasitiformes) or fused to (Acariformes) the body wall.
   IV broad (subequal to width of stigmastigma:
   the opening to the tracheal system.
   ); corniculicorniculus:
   (pl. corniculi) (also, external malae) a usually horn-like process (sometimes toothed, bifurcate, trifurcate, spine-like, spatulate, or membranous) on the subcapitulum of parasitiform mites that usually supports the salivary styli.  A toothed corniculus could be confused with a rutellum, a possibly homologous structure in Acariformes and Opilioacarida. Phytoseiid image is spatulate corniculus.
   slender, acute; rows of deutosternal denticlesdeutosternal denticles:
   rows of small teeth-like projections (often irregular and sometimes reduced to a single tooth) running transversely across the deutosternal groove and sometimes onto the lateral faces of the subcapitulum.
   narrow, in deep trough; epistomegnathotectum:
   (= epistome, tectum) an often membranous dorsal projection of the anterior margin of the basis capitulum in Mesostigmata; often diagnostic at family-, genus- or species-levels; also often difficult to see without high magnification and good optics.
   convex, smooth; movable chelachela:
   a pincer, as in a pseudoscorpion's distal pedipalpal segments.
   of female unidentate.............................. Proctogastrolaelaps
   - Ventralventral:
   relating to the lower or under side; opposed to dorsal.
   area not sclerotized, only small anal shieldanal shield:
   in Mesostigmata, a ventral shield bearing the anal opening and circumanal setae (po, pa), but without any ventral setae or pores (lyrifissures) [see ventrianal shield]
   with 3 circumanal 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.............................. 3

3. Fixed chelachela:
   a pincer, as in a pseudoscorpion's distal pedipalpal segments.
   of female and nymphs with pointed or rounded flange-like projection distally; leg IV with 1 or 2 erect macrosetae on telotarsustelotarsus:
   (= acrotarsus, apicotarsus) a distal division of the tarsus.  
   (pd2, +/- ad2); 3rd pair of sternal poressternal pores:
   (designations = stp or iv) in Mesostigmata, the lyrifissures in the intercoxal region; stp1-2 often occur on the sternal shield and stp3 is associated with the metasternal setae on a combined sternal-metasternal shield, on a separate sternal platelet, or in soft cuticle.
   absent.............................. Mucroseius
   - Fixed chelachela:
   a pincer, as in a pseudoscorpion's distal pedipalpal segments.
   without distaldistal:
   towards the free end of an appendage.
   flange-like projection; leg IV usually without macrosetae; 3rd pair of sternal poressternal pores:
   (designations = stp or iv) in Mesostigmata, the lyrifissures in the intercoxal region; stp1-2 often occur on the sternal shield and stp3 is associated with the metasternal setae on a combined sternal-metasternal shield, on a separate sternal platelet, or in soft cuticle.
   usually present.............................. 4

4. Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield of adults with pair of deep midlateral incisions, lacking 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.
   z3 on podonotalpodonotal:
   relating to the dorsal podosoma, the region of the idiosoma over the legs.
   region; movable chelachela:
   a pincer, as in a pseudoscorpion's distal pedipalpal segments.
   with 0 or 1 tooth; female without metasternal plates.............................. 6
   - Dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield of adults entireentire:
   a shield or sclerite with a continuous margin without incisions.
   , usually with 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.
   z3 on podonotalpodonotal:
   relating to the dorsal podosoma, the region of the idiosoma over the legs.
   region; movable chelachela:
   a pincer, as in a pseudoscorpion's distal pedipalpal segments.
   with 3 teeth; with or without metasternal plates.............................. 5

5. Adults with 7–13 pairs of marginal (r–R) 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.
   on soft lateral cuticle (rarely fewer if some r–R 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.
   lacking); female with 14–15 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.
   on opisthonotalopisthonotal:
   dorsal opisthosoma.
   region of dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield and lacking metasternal plates (except in Orolaelaps).............................. Melichares
   - Adults with 1–4 pairs of posteriorposterior:
   the back part of the body or towards that region in comparison, e.g., 'posterior to'.
   marginal (R) 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.
   on soft ventro-lateral cuticle, all others on edge of dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield; female with 18–22 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.
   on opisthonotalopisthonotal:
   dorsal opisthosoma.
   region of dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield; female usually with metasternal plates.............................. Proctolaelaps

6. Movable chelachela:
   a pincer, as in a pseudoscorpion's distal pedipalpal segments.
   unidentate; female with 1st pair of sternal 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.
   on soft cuticle in front of sternal shieldsternal shield:
   a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
   ; male with separate ventralventral:
   relating to the lower or under side; opposed to dorsal.
   & anal shields; male leg II with tarsal 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.
   pv1 unmodified.............................. Xanthippe
   - Movable chela edentateedentate:
   with out teeth; usually referring to chelicerae.
   ; female with first pair of sternal 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.
   on sternal shieldsternal shield:
   a shield in the anterior intercoxal region of parasitiform mites that bears one or more pairs of sternal setae.
   ; male usually with consolidated 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.
   ; male leg II with apicalapical:
   at the tip of a structure
   tarsal 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.
   pv–1 slightly to conspicuously thickened.............................. 7

7. Tibiaetibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   III and IV with 9 and 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.
   respectively (pl2 present); dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield with 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.
   s6; female with hyaline anterioranterior:
   the front part of the body or towards that region in comparison, e.g., 'anterior to'
   margin of epigynialepigynal:
   (also epigynial) of or relating to the female genital opening or a shield protecting it.
   shield rounded, and with genital 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.
   on lateral edges of this shield; male tarsustarsus:
   (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
   II with 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.
   pv–1 knob- or spine-likespine-like:
   a seta or other structure that resembles a thorn or spine; spiniform.
   , and tarsustarsus:
   (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
   III with 1–3 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.
   (always av2) knob-like; male spermatodactylspermatodactyl:
   (also spermadactyl) the 'sperm finger' on the chelicerae of male dermanyssine Mesostigmata used to transfer sperm to the secondary sperm system in the female; spermatodactyls take various forms, from simple finger-like processes to very long, contorted structures.  
   directed anteriorly.............................. Tropicoseius
   - Tibiaetibia:
   (pl. tibiae) the leg segment between the genu and the tarsus.
   III and IV with 8 and 9 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.
   respectively (pl2 absent); dorsaldorsal:
   relating to the upper or back side; opposed to ventral.
   shield lacking 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.
   s6; female with hyaline anterioranterior:
   the front part of the body or towards that region in comparison, e.g., 'anterior to'
   margin of epigynialepigynal:
   (also epigynial) of or relating to the female genital opening or a shield protecting it.
   shield usually truncated or emarginated, and with genital 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.
   on soft cuticle flanking this shield; male tarsustarsus:
   (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
   II with 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.
   pv1 but slightly thickened, and tarsustarsus:
   (pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
   III without modified 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.
   ; male spermatodactylspermatodactyl:
   (also spermadactyl) the 'sperm finger' on the chelicerae of male dermanyssine Mesostigmata used to transfer sperm to the secondary sperm system in the female; spermatodactyls take various forms, from simple finger-like processes to very long, contorted structures.  
   directed posteroventrally.............................. Rhinoseius

Ecology and distribution

Flower-inhabiting mites phoretic on hummingbirds or beetles (Xanthippe).

References

• Colwell and Naeem 1994Colwell and Naeem 1994:
  Colwell RK, Naeem S. 1994. Life-history patterns of hummingbird flower mites in relation to host phenology and morphology. pp. 23–44. In: Houck MA, ed. Mites: Ecological and evolutionary analyses of life-history patterns. Chapman & Hall: New York.
• Krantz 1986Krantz 1986:
  Krantz GW. 1986. A manual of acarology [2nd ed., emended 1986]. Oregon State University Book Stores, Corvallis.
• Lindquist and Evans 1965Lindquist and Evans 1965:
  Lindquist EE and Evans GO. 1965. Taxonomic concepts in the Ascidae, with a modified setal nomenclature for the idiosoma of the Gamasina (Acarina: Mesostigmata). Memoirs of the Entomological Society of Canada 47: 1-64
• Naskrecki and Colwell 1995Naskrecki and Colwell 1995:
  Naskrecki P and Colwell RK. 1995. New genus and two new species of Melicharini from Venezuela (Acari: Mesostigmata: Ascidae). Annals of the Entomological Society of America 88: 284-293.
• Naskrecki and Colwell 1998Naskrecki and Colwell 1998:
  Naskrecki P and Colwell RK. 1998. Systematics and host plant affiliations of hummingbird flower mites of the genera Tropicoseius Baker and Yunker and Rhinoseius Baker and Yunker (Acari: Mesostigmata: Ascidae). Thomas Say Publications in Entomology, Entomological Society of America. 185 pp.
• Ohmer et al. 1991Ohmer et al. 1991:
  Ohmer C, Fain A, and Schuchmann K-L. 1991. New ascid mites of the genera Rhinoseius Baker and Yunker, 1964, and Lasioseius Berlese, 1923 (Acari: Gamasida: Ascidae) associated with hummingbirds or hummingbird-pollinated flowers in southwestern Columbia. Journal of Natural History 25: 481-497.
• OConnor et al. 1997OConnor et al. 1997:
  OConnor BM, Colwell RK, and Naeem S. 1997. The flower mites of Trinidad III. The genus Rhinoseius (Acari: Ascidae). Miscellaneous Publications, Museum of Zoology, University of Michigan 184: 1-32.