Glossary of Acarine Morphological Terms

A work in progress © DE Walter 2004

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

• abdomen - loosely used term usually referring to the opisthosoma or hysterosoma in mites.

• abjugal plane (furrow) - a mostly theoretical division between the podosoma and gnathosoma.

• acetabulum - a concave cavity in the body wall where a leg or other structure is inserted; in brachypyline oribatids they may be cavities where the trochanter articulates with the coxae (fused to the body wall) and may contain tracheal stigmata; the genital opening and papillae of acariform mites are contained within an acetabulum; also, the concave portion of a ball and socket joint.

• acrotarsus (= apicotarsus) - distal subdivision of the tarsus, usually of tarsus I (NB - not to be confused with the ambulacral stalk or pretarsus).

• AD - adanal segment in acariform mites; added on the deutonymph, see anamorphosis.

• adanal plate (or region) - sclerites or sclerotized fields laterad the anal region; usually used in oribatid mite taxonomy and bearing adanal setae.

• aggenital (also adgenital) plate (or region) - sclerites or sclerotized fields on either side of the genital opening.

• alveolus - a setal socket (also a single depression in alveolate ornamentation).

• ambulacrum - the claws and empodium of the apotele or pretarsus (technically including the ambulacral stalk [also called pretarsus] and apotele [empodium and claws]).

• AN - anal segment in acariform mites; added on the protonymph, see anamorphosis.

• anal shield - in Mesostigmata, a ventral shield bearing the anal opening and circum anal setae, but without any ventral setae or pores (lyrifissures) [see ventrianal shield].

• anamorphosis - the addition of body segments (and their structures) during ontogeny; in Acariformes, additions occur behind the anal opening (pseudanal segment in the larva): anal (AN) in the protonymph, adanal (AD) in the deutonymph, peranal (PA) in the tritonymph.

• anarthric - an unjointed subcapitulum without a labiogenal suture.

• anogenital region - the ventral region encompassing the genital, aggenital, anal and adanal sclerites in oribatid mites.

• antiaxial - away from the axis of the body (midline), e.g. the outer or lateral face of a chelicera (also abaxial).

• apicotarsus (= acrotarsus) - distal subdivision of the tarsus, usually of tarsus I.

• apodeme - sclerotized invagination of the cuticle, often at the margin of a plate, that serves as attachment site for muscles.

• apotele (= pretarsus) - the most distal leg segment, often consisting of an empodium and a pair of claws.

• area porosae - usually round to oval aggregations of pore-like areas of the cuticle; usually referring to the octotaxic system of the Oribatida.

• articulation - a region of differentiated cuticle joining two parts of an exoskeleton; a joint, scissure or furrow.

• aspis - a sclerotized shield over the aspidosoma.

• aspidosoma - the anterior dorsal region of the prosoma in acariform mites.

• astegasime - having the chelicerae exposed dorsally: the rostral tectum is reduced or absent (see stegasime), as in many Prostigmata, Astigmata and some early derivative oribatids.

• B

• basilar piece - the median internal structure with which the claws articulate in the ambulacrum of Mesostigmata.

• basifemur - a basal subdivision of the femur.

• basitarsus - a basal subdivision of the tarsus.

• basis capitulum - the sclerotized ring around the base of the gnathosoma in parasitiform mites.

• bothridial sensillum (= trichobothrium) - an often elaborately modified seta set in a cup-like base; forms include filiform, ciliate, pectinate or variously thickened or clubbed (bat-like to globose to capitate).

• bothridial seta - prodorsal seta bo (also sci or s1) in Acariformes.

• bothridium - the cup-like base of a bothridial sensillum.

• brachypyline - having separate genital and anal plates surrounded by a large ventral plate (composed of aggenital and adanal elements); usage usually restricted to traditional oribatid mites (see macropyline).

• brachytracheae - thick, elongated and porose tube-like invaginations in the cuticle of some oribatid mites.

• C

• camerostome - a recess under the rostral tectum that allows retraction of the chelicerae and palps of oribatid mites and that is sealed by the subcapitulum when retracted.

• capitulum (pl. capitula)  (= gnathosoma) - the anteriormost part of a mite, composed of the cheliceral and pedipalpal segments and separated from the body (idiosoma) by a ring of soft cuticle.

• carina - a longitudinal ridge.

• cerotegument - a layer of wax or cement on top of the cuticle, often thin and inconspicuous, but sometimes very thick, ornamented, and obscuring the underlying cuticle; thick ceroteguments often can be peeled off to expose a very different-looking mite.

• chela - a pincer, as in a pseudoscorpion's distal pedipalpal segments.

• chelate - pincer-like, as in a crab's claws, a scorpion's pedipalps or many chelicerae.

• chelate-dentate - pincer-like chelicerae with teeth.

• chelate-serrate - pincer-like chelicerae with a row of saw-like teeth (also serrate).

• chelicera - a limb on the presumed first body segment in chelicerate arthropods, the primary mouthparts.

• chelicerate - a member of the Chelicerata.

• circumcapitular furrow - the flexible articulation joining the capitulum (gnathosoma) to the reminder of the body (idiosoma).

• circumgastric scissure (furrow) - the flexible articulation that joins the notogaster to the ventral plate in brachypyline oribatid mites.

• Claparede's Organ - the presumed homologue of the genital papillae found between legs I-II in the larvae of many acariform mites (= urstigma).

• clunal setae - the most posterior pair of median opisthonotal setae in Mesostigmata: setae J5.

• companion seta - a seta closely associated with a solenidion, sometimes sharing the same insertion.

• corniculus (pl. corniculi) - a usually horn-like process (sometimes toothed, bifurcate, trifurcate, spine-like, 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.

• costula - a longitudinal ridge or set of ridges on the prodorsum of some oribatid mites, similar to lamellae but without a projecting edge or cusp.

• coxa - the basal segment of the leg, articulating with (Parasitiformes) or fused to (Acariformes) the body wall.

• coxisternum - floor of the podosoma that serves to support the legs, composed of the fused coxae (epimera I-IV).

• crista - a crest-like or tooth-like ridge, especially  in oppioid oribatid mites.

• crista metopica - the often narrow prodorsal sclerite bearing 1-2 pairs of trichobothria in parasitengone mites.

• D

• deficient - in relation to setae, reduced from a presumed holotrichous number.

• denticles - tooth-like processes on the subcapitula of ticks and mesostigmatans.

• deutonymph - the second nymphal stage.

• deutosternum - the sternum of the second body segment (pedipalps).

• diarthric - a subcapitulum with a +/- transverse articulation that reaches the lateral margin at the base of the palp.

• dichoid - appearing to be divided into two by a flexible sejugal suture (Acariformes).

• disjugal plane (furrow) - the plane separating the ancestral prosoma and opisthosoma, usually not clearly present in mites and confounded with the sejugal furrow.

• dorsal - relating to the upper or back side; opposed to ventral.

• dorso-sejugal suture (dorsosejugal groove) - a suture marking the fusion of the prodorsum and notogaster; the anterior portion of the circumgastric scissure.  NB - this term is often misapplied to a flexible junctire.

• dorsum - the upper or back side; opposed to venter.

• duplex setae - a pair of setae or a seta and a solenidion sharing the same insertion.

  E

• Endeostigmata - a paraphyletic assemblage of early derivative sarcoptiform mites that has often been misplaced in the Prostigmata.  Ten families are currently recognized, including the widespread and common Nanorchestidae, Bimichaeliidae, Alicorhagiidae, and Terpnacaridae.  Most endeostigmatans are fungivores, algivores or feed on minute, soft-bodied invertebrates such as nematodes.

• endopodal shield - usually narrow, strap-like sclerites produced around the bases of the coxae in Mesostigmata; the anterior endopodal shields are often fused to the sternal shield.

• epicoxal seta - a minute, usually peg-like seta on the dorsal face of the palpcoxa (ep) or coxae of legs I (ep1) in some acariform mites.

• epigynal (also epigynial) - of or relating to the female genital opening or a shield protecting it.

• epigynum (also epigynium)- the external genital opening in the female; also used for the ovipore in Dermanyssina (which have a secondary female genital system).

• epimere  (pl. epimera) (also epimeron) - in oribatid mites, a sclerotized coxal field; in Astigmata, anterior coxal apodeme.

• epimerite - in Astigmata, the posterior coxal apodeme.

• eupathidium (pl. eupathidia) - a hollow seta with a pore at its tip and found on the palptarsus or leg I tarsus of many acariform mites; probably a chemoreceptor.

• exopodal shield - usually narrow, strap-like sclerites produced around the lateral bases of the coxae in Mesostigmata; sometimes fused to the peritrematal shield.

• external scapular seta - prodorsal seta sce (also se or s2) in Acariformes.

• external vertical seta - prodorsal seta ve (also se or s2) in Acariformes.

• exuviae (pl. exuviae) - the outer layer of skin not recycled during a molt; empty exuviae are a sign of previous mite development when found on a product; some oribatid mites retain the dorsal notogasteral portion of exuviae as a pagoda-like pile of scalps.  (NB: the use of 'exuvia' as a singular makes no more sense than 'cloth' for 'clothes'.)

  F

• famulus - a hollow seta-like structure located near the base of the dorsum of tarsus I, especially in oribatid mites.

• femur (pl. femora) - major leg segment between trochanter and genu; often subdivided into a basifemur and a telofemur.

• G

• geniculate - with an elbow- or knee-like bend.

• genital papillae - 1-3 pairs of finger-like projections, usually retracted into in the genital vestibule, or sessile disks around the genital opening of many acariform mites; thought to be osmoregulatory structures; modified or multiplied and dispersed over the body in many freshwater mites.

• genital vestibule - the  ventral chamber containing the genital papillae and genital opening and closed by a pair of genital valves.

• genu (pl. genua) (= patella) - the 4th leg segment, between the femur and tibia.

• gnathosoma (= capitulum) - - the anteriormost part of a mite or ricinuleid, composed of the cheliceral and pedipalpal segments and separated from the body (idiosoma) by a ring of soft cuticle.

• gnathotectum (= epistome) - 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.

• Grandjean system - the primary system for designation of hysterosomal setae used in the Acariformes.  Hypothesized segments (anterior to posterior) are C, D, E, F, H, PS (pseudanal), AD (adanal), AN (anal) and PA (peranal) (see anamorphosis).  'G' is not used to avoid confusion with the genital segment, which is treated separately.  Setae are designated from the midline to the sides from 1-x, e.g. c1, c2, c3, c4 (also cp).

  H

• holoid - lacking flexible cuticle between legs II-III.

• humeral process - any fixed projection in the humeral region; sometimes confused with pteromorphs.

• humeral seta - a seta in the humeral ('shoulder') region, often projecting at a more or less right angle to the body; usually seta r3 in Mesostigmata and c3 or c4 (cp) in Acariformes.

• hypostomal groove (or gutter) - median longitudinal depression on the ventral gnathosoma in Mesostigmata.

• hypostome - the anterior part of the subcapitulum.

• hysterosoma - idiosoma behind the sejugal suture (plane) between legs II-III; opposed to the proterosoma.

  I

• idiosoma (= body) - the main body tagma of mites, containing the opisthosoma and part of the prosoma.

• internal scapular seta - prodorsal seta sci (also si or s1) in Acariformes.

• internal vertical seta - prodorsal seta vi (also v1) in Acariformes.

  J

• j-series - In the Lindquist and Evans system used in the Mesostigmata, the most median longitudinal row of prodorsal setae running from the anterior vertical setae j1 to setae j6 at or near the posterior margin of the pronotal shield or region.

• J-series - In the Lindquist and Evans system used in the Mesostigmata, the most median longitudinal row of opisthonotal setae running from the anterior setae J1 to the clunal setae J5 at or near the posterior margin of the opisthonotal shield or region.

• K

• krobylophore - cuticular, duct-like structure in ticks.

  L

• labiogenal articulation - a flexible juncture on the venter of the subcapitulum that allows the paired anterior sections (genae) to articulate with the base (mentum); see anarthric, stenarthric, diarthric.

• lamella - a longitudinal projection on the prodorsum of many oribatid mites that protects legs I when they are retracted; lamellae usually arise near the base of the bothridia and terminate with a projecting lamellar seta (often on a free cusp).

• larva - the second instar in acariform mites having a complete ontogenetic sequence, but the first instar in most mites (where the prelarva is absent); hexapod (unless adults have less than 6 legs, as in Eriophyoidea); may be feeding or non-feeding.

• lateral - to the side.

• latigynal (also latigynial) shields - a pair of sclerites laterad the mesogynal shield in some female parasitiform mites that help protect the genital opening; usually bearing one or more pairs of setae and sometimes fused to other genital or ventral elements.  The single female genital shield in the Gamasina may represent a fusion of the latigynal and mesogynal shields.

• lenticulus - a light sensitive structure, with or without a lens, on the anterior opisthosoma of some oribatids.

• Lindquist-Evans system - the system of setal signatures proposed by Lindquist & Evans (1965) and the dominant nomenclature used in the Mesostigmata in the more modern literature.  Dorsally, the setae are designated by minor (on the pronotum or podonotum) and major (on the opisthonotum) Arabic letters representing longitudinal rows (from the midline to the lateral margin, j-J, z-Z, s-S, r-R, and an additional UR or submarginal row posteriorly) and Arabic numbers designating transverse rows (of hypothesized segments) from 1-6 on the pronotum and 1-5 (or higher in the UR-series) on the opisthonotum.  See also, modifications by Lindquist (1994) and Lindquist & Moraza.
  
    Ventrally, idiosomal setae are treated as belonging to three regions: the sternal (intercoxal), the ventral, and the anal.  Three pairs of sternal setae are present in the larva (st1-3); the genital seta st5 is added in the protonymph; and the 'metasternal seta st4 is added in the deutonymph.  The 'metasternal' seta probably has more to do with the genital than the sternal region and is the only 'sternal' seta that is sometimes not expressed.  The ventral region has up to three longitudinal rows (Jv, Zv, Lv) with 1-5 transverse row designations.  The anal region has a pair of paranal setae (pa) and an unpaired postanal seta (po).

• lyrifissure - a cuticular proprioreceptor (deformation sensing) structure; under light microscopy these structures may look like slits in hardened cuticle or compressed-T's, or in soft cuticle, a round pit (cupule).

  M

• macropyline - having separate adgenital and adanal plates and genital and anal shields such that most of the post-coxal venter is occupied by the two paired series of shields; usage usually reserved to traditional oribatid mites (see brachypyline).

• median - to the midline of the body.

• mental tectum - a projection of the mentum on some oribatid mites with diarthric subcapitula.

• mentum (pl. menta) - the basal section of the subcapitulum in oribatid mites with a labiogenal articulation.

• mesogynal (also mesogynial) shield - an unpaired median sclerites in some female parasitiform mites that helps protect the genital opening; usually nude and sometimes fused to other genital or ventral elements.  The single female genital shield in the Gamasina may represent a fusion of the latigynal and mesogynal shields.

• metasternal setae - In Mesostigmata, the intercoxal setae (designated st4) added in the deutonymph, often are borne on metasternal platelets, and sometimes on the sternal shield or in soft cuticle in the adult female; rarely absent.

• metasternal shield (platelet) - small, usually teardrop to subtriangular shields bearing the metasternal setae (st4); sometimes fused to the sternal shield or the endopodal shields.

  N

• naso - a nose-like protrusion of the idiosomal rostrum that projects over the chelicerae in early derivative Acariformes and may bear a pair of setae (ro = vi) dorsally and some times a median eye(s) ventrally.

• neotrichous - having setae not present in the ancestral condition, 'new setae'; often a highly subjective assessment.

• notogaster - the dorsal hysterosoma, or in a more specific sense, the shield covering the dorso-lateral aspects of the hysterosoma in many oribatid mites.

  O

• ocellus (pl. ocelli) - a simple eye.

• octotaxic system - the set of four pairs of porose or sacculate dermal glands on the notogaster of poronotic brachypyline oribatid mites.

• opisthonotal - dorsal opisthosoma.

• opisthosoma (= abdomen) - the posterior body division in arachnids.

  P

• PA - peranal segment in acariform mites; added on the tritonymph, see anamorphosis.

• palp (= pedipalp) - the second pair of limbs in arachnids.

• palptarsal apotele (= palp apotele) - the most distal segment of the palp; absent in Acariformes, claw-like in Opilioacarida, and a subdistal, tined structure in the Mesostigmata.

• palptibial claw - a claw-like seta on the palptibia of some Prostigmata that forms a chelate structure with the palp tarsus, the palpclaw complex.

• paranal setae - the pair of seta inserted laterad the anal opening in the Mesostigmata; usually designated pa.

• paravertical setae - in the Mesostigmata, the anteriormost pair of setae in the z-series, setae z1; usually on the anterolateral edge of the pronotum and inserted across a lyrifissure from the vertical setae j1.

• paraxial - against the axis of the body (also adaxial), e.g. the inner face of the chelicera.

• patrocinium - paralabral style in some Mesostigmata (e.g. Macrochelidae).

• pedipalp (= palp) - the second pair of limbs in arachnids.

• pedofossa (pl. pedofossae) (= fossae pedales, fovae pedales) - recesses into which the legs can be withdrawn.

• pedotectum (pl. pedotecta) - a scale-like tectum arising around the insertion of legs I or II in some armored oribatid mites that covers the insertion of the leg and sometimes forms a protected space into which the legs can be withdrawn.

• peritreme - a groove or gutter on the surface connecting to the stigmatal opening.

• platytracheae - porose lamelliform pouch-like invaginations in the cuticle of some oribatid mites.

• podonotal - relating to the dorsal podosoma.

• podonotum - the dorsal podosoma.

• podosoma - region of the idiosoma bearing the legs (body segments III-VI); according to currently accepted theory, in acariform mites the dorsal portion of this division has regressed and only the leg bases are included.

• postanal seta - the unpaired median seta inserted posterior to the anal opening in the Mesostigmata; usually designated po.

• prelarva - the first instar in acariform mites having a complete ontogenetic sequence, but absent in derived Prostigmata and Parasitiformes (except Opilioacarida); incompletely formed, without functional mouthparts, often retained within the egg shell or just extruding from it, and usually inactive; hexapod or apodous.

• propodosoma - a subdivision of the podosoma bearing legs I-II.

• protonymph - the first nymphal instar, usually octopod.

• prosoma (= cephalothorax) - the anterior body region in arachnids; usually not distinct in mites.

• proterosoma - the body anterior to the sejugal plane (suture); complementary to the hysterosoma and only used in Acariformes.

• PS - pseudanal segment in acariform mites; 'anal' segment in the larva, see anamorphosis.

• pseudostigmatic organ - an obsolete term for the bothridial sensillum or trichobothrium, especially in oribatid mites.

• pteromorph - wing-like lateral extensions of the body in oribatid and tarsonemid mites.

• ptychoidy - the ability of some oribatid mites to withdraw the legs between two body regions like a penknife being closed and resulting in a seed-like appearance.

  Q

• quiescent - at rest, usually referring to an inactive developmental stage, e.g. the inactive immatures of acariform mites during the intermolt period.

  R

• Rostral-lamellar system - a system of designations for the prodorsal setae in Acariformes based on Grandjean's system as applied to the Oribatida. These setae are not added ontogenetically; therefore, homologies are based on position and subject to various interpretations.  Each pair of setae may represent one of the 6 presumed prosomal segments; however, Grandjean believed that the dorsal podosoma and their setae were lost in acariform mites, in which case the prodorsal setae would derive from only cheliceral and pedipalpal segments.  The designations are: rostral (ro), lamellar (le), bothridial (bo), anterior exobothridial (exa, also xa), interlamellar (in), and posterior exobothridial (exp, also xp).  When present, setae bo are usually expressed as trichobothria (except in Nematalycoidea, Astigmata, some Oribatida, and many Prostigmata), and setae ro or le are sometimes trichobothrial).
  
  In Endeostigmata, the Vertical-scapular system is more commonly used (vi, ve, sci, sce, in, exp, respectively).  Prodorsal setae exp, in or both are often lost.  In the Prostigmata, the prodorsal setae are represented at their maximum by the interior and exterior vertical (vi, also v1; ve, also v2) and internal and external scapular setae (sci, also s1; sce, also s2) (a possible exception exists in Pilorhagidia which has 5 pairs).  In Astigmata, the traditional designations follow those used in the Prostigmata; however, the purported internal scapular setae (sci or si) actually are in.

• rostral seta - the anteriormost pair of prodorsal setae or an unpaired median seta (Nematalycoidea) in the Acariformes; when a naso is present, it often carries the rostral setae; various designations: ro,  vi, v1.

• rostral tectum (also rostrum) - a prodorsal tectum that projects over at least the base of the chelicerae in acariform mites, often covering most of the capitulum; not to be confuse with the basis capitulum of parasitiform mites.

• rostrum - the anteriormost portion of the idiosoma, especially when it projects over the bases of the chelicerae (see naso).

• r-series - In the Lindquist and Evans system used in the Mesostigmata, the longitudinal row of marginal prodorsal setae laterad the s-series and running from the anterior setae r1 (usually absent) to setae r6 at or near the posterior margin of the pronotal shield or region.  Setae r3 and r4 are in the humeral angle and often project at right angles to the body; other r-series setae are often in the soft cuticle.

• R-series - In the Lindquist and Evans system used in the Mesostigmata, the longitudinal row of opisthodorsal setae laterad the S-series, mesad the UR-series, and running from the setae R1 to setae R6 (sometimes more) at or near the lateral margin of the opisthonotal region.  R-series setae are usually inserted in soft cuticle.

• rutellum (pl. rutella) - hypertrophied setae on the hypostome, often toothed; not to be confused with a corniculus (although possibly a homologue).

  S

• saccule - invaginated porose organs resembling small sacks and opening to the surface by a small pore (see octotaxic system).

• salivary stylet - external ducts protected by the corniculi in Mesostigmata.

• scalps - notogastral portions of exuviae retained by some oribatid mites, often as a pagoda-like pile of larval through tritonymphal exuviae, although one or more of these may fall off during handling of specimens.  Scalp is also used to indicate the macerated cuticle of a mite that has been cleared and mounted on a microscope slide.

• scissure - a band of unsclerotized cuticle between two plates; an elongate articulation.  NB - suture (an inflexible juncture) is often used inappropriately for what would be better termed a scissure.

• sejugal suture (or plane) - a division cutting the acariform mite idiosoma between legs II-III.

• sensillum (pl. sensilla) (also sensilla, sensillae; 'sensillus' is incorrect) - a sensory structure;  sensilla is often used for the bothridial seta in Acariformes.

• solenidion (pl. solenidia) - a hollow chemosensory seta appearing to have transverse rows of minute pores (actually pore canals) under light microscopy, (the transverse pattern is usually not apparent in SEM); often bulbous or otherwise modified; sometimes associated with a companion seta.

• spermatophore - any structure that carries a packet of sperm, including complex stalks deposited on substrate by male acariform mites and flask-like structures carried on the chelicerae of male mesostigmatans.

• spermatodactyl - 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.

• spermatotreme - a slit-like opening on the movable digit of male Parasitidae that grasps the neck of the spermatophore during sperm transfer.

• spinae adnatae - a pair of tooth-like projections on the anterior margin of the notogaster of damaeid oribatids.

• s-series - In the Lindquist and Evans system used in the Mesostigmata, the longitudinal row of prodorsal setae laterad the z-series, mesad the r-series, and running from the anterior setae s1 to setae s6 at or near the posterior margin of the pronotal shield or region.

• S-series - In the Lindquist and Evans system used in the Mesostigmata, the longitudinal row of opisthodorsal setae laterad the Z-series, mesad the R-series, and running from the setae S1 to setae S5 at or near the postero-lateral margin of the opisthonotal shield or region.

• stase - equivalent to an instar in most mites; if no additions are made during a molt, then several instars may occur in one stase.

• stegasime - having the chelicerae protected dorsally by a rostral tectum (see astegasime), as in most oribatid mites.

• stenarthric - a subcapitulum with a triangular mentum and oblique labiogenal sutures; probable primitive condition in Acariformes.

• sternal setae - In Mesostigmata, the five pairs of setae in the intercoxal region designated st1-5; st1-3 are present in the larvae and usually are borne on a sternal shield in the adult female; st4, the metasternal setae, are added in the deutonymph, often are borne on metasternal platelets, and sometimes on the sternal shield; st5, the genital setae, are added in the protonymph and usually borne on or are inserted laterad the epigynal shield in the adult female.

• supracoxal seta - an often inflated or otherwise elaborated dorsal coxal seta in astigmatans associated with the supracoxal gland opening.

• suture - an inflexible juncture between two body parts; line of fusion between two formerly separate body parts or regions.  This term is often misused for flexible articulations.

  T

• tarsal apotele (= pretarsus) - the most distal segments of legs and palps bearing the claws and empodium.

• tarsus - the subdistal leg segment between the tibia and the pretarsus (apotele).

• tectum - a shelf-like projection of the cuticle [see gnathotectum].

• telofemur - a distal division of the femur.

• telotarsus (= acrotarsus, apicotarsus) - a distal division of the tarsus.

• tibia (pl. tibiae) - the leg segment between the genu and the tarsus.

• tracheae - the long, filamentous tubes that ramify through the body of some mites for the exchange of gases.

• Tragardh's organ - a flat, finger-like paraxial projection on the chelicerae of some oribatid mites; usually difficult to see unless the chelicerae are dissected out.

• trichobothrium (pl. trichobothria) (= bothridial sensillum) - an often elaborately modified seta set in a cup-like base; forms include filiform, ciliate, pectinate or variously thickened or clubbed (bat-like to globose or capitate).

• tritonymph - the third, and final, nymphal instar present in Opilioacarida, Holothyrida, Argasidae, and many Acariformes.

• tritosternum - the sternum of the 3rd body segment (between legs I); produced as a biflagellate structure in Mesostigmata.

• trochanter - the leg segment between the coxa and the femur.

• tutorium (pl. tutoria) - a ridge on the lateral prodorsum of oribatid mites, ventral and more or less parallel to the lamella and protecting legs I when retracted.

  U

• unideficient - lacking one seta from the assumed holotrichous condition.

• urstigma (pl. urstigmata) - the presumed homologue of the genital papillae found between legs I-II in the larvae of many acariform mites (= Claparede's organ).

  V

• ventral - relating to the lower or under side; opposed to dorsal.

• ventral plate - a sclerotized plate covering the ventral region of the opisthosoma in brachypyline oribatid mites and separated from the notogaster by the circumgastric scissure; also any plate in the ventral region.

• ventral region - in Mesostigmata, the area between the genital and anal regions.

• ventral setae - in the Lindquist and Evans system used in the Mesostigmata, the ventral region has up to three longitudinal rows (Jv, Zv, Lv) with 1-5 transverse row designations.

• ventral shield - in Mesostigmata, any shield or shields in the ventral region; often fused with the anal shield to form a ventrianal shield.

• venter - the lower or under side; opposed to dorsum.

• ventrianal 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].

• Vertical-scapular system - a system of designations for the prodorsal setae in Acariformes, especially in the Endeostigmata and Prostigmata.  Prodorsal setae exp, in or both are often lost.  In the Prostigmata, the prodorsal setae are represented at their maximum by the interior and exterior vertical (vi, also v1; ve, also v2) and internal and external scapular setae (sci, also s1; sce, also s2) (a possible exception exists in Pilorhagidia which has 5 pairs).  In Astigmata, the traditional designations follow those used in the Prostigmata; however, the purported internal scapular setae (sci or si) actually are in.  In Oribatida, the Rostral-lamellar system is more commonly used (ro, le, bo, exa, in, exp, respectively).

• vertical setae - in the Mesostigmata, the anteriormost pair of median setae in the j-series, setae j1; usually projecting over the gnathosoma, often modified, and inserted across a lyrifissure from the paravertical setae z1.  In the Acariformes, setae sci and sce (see vertical-scapular system).

  W

• With's organ - a membranous structure on the anterior margin of the subcapitulum in Opilioacarida.

  X

• xylophage - feeding on wood.

• Y

• Y-tube olfactometer - an experimental devise, typically a tube with three arms in a Y-shape, often used for testing of the response of phytoseiid mites to chemical scents.

  Z

• z-series - In the Lindquist and Evans system used in the Mesostigmata, the longitudinal row of prodorsal setae laterad the j-series, mesad the s-series, and running from the anterior paravertical setae z1 to setae z6 at or near the posterior margin of the pronotal shield or region.

• Z-series - In the Lindquist and Evans system used in the Mesostigmata, the longitudinal row of opisthodorsal setae laterad the J-series, mesad the S-series, and running from the setae Z1 to setae Z5 at or near the posterior margin of the opisthonotal shield or region.  Setae Z5 are often elongate and project posteriorly well beyond the body margin.