Glossary of spider terms

This glossary describes the terms used in formal descriptions of spiders; where applicable these terms are used in describing other arachnids. 

Terms

A

Abdomen or opisthosoma: One of the two main body parts (tagmata), located towards the posterior end; see also Abdomen: Other animals

Accessory claw: Modified setae at the tip of the tarsus in web-building spiders; used with tarsal claws to grip strands of the web

Anal tubercle: A small protuberance (tubercule) above the spinnerets through which the anus opens

Apophysis (plural apophyses): An outgrowth or process changing the general shape of a body part, particularly the appendages; often used in describing the male pedipalp → retrolateral tibial apophysis

Atrium (plural atria): An internal chamber at the entrance to the copulation duct in female haplogyne spiders

B
Bidentate: Having two teeth

Book lungs: Respiratory organs on the ventral side (underside) of the abdomen, in front of the epigastric furrow, opening through narrow slits; see also Book lungs

Branchial operculum: → operculum

Bulbus → palpal bulb

C
Calamistrum (plural calamistra): Modified setae (bristles) on the metatarsus of the fourth leg of spiders with a cribellum, arranged in one or more rows or in an oval shape, used to comb silk produced by the cribellum; see also Calamistrum

Caput (plural capita): → cephalic region

Carapace: A hardened plate (sclerite) covering the upper (dorsal) portion of the cephalothorax; see also Carapace

Carpoblem: The principal tibial apophysis on the male pedipalp; also just called the tibial apophysis

Cephalic region: The front part of the cephalothorax, separated from the thoracic region by the cervical groove

Cephalothorax or prosoma: One of the two main body parts (tagmata), located towards the anterior end, composed of the head (cephalic region or caput) and the thorax (thoracic region), the two regions being separated by the cervical groove; covered by the carapace and bearing the eyes, legs, pedipalps and mouthparts

Cervical groove: A shallow U-shaped groove, separating the cephalic and thoracic regions of the carapace

Chelate: A description of a chelicera where the fang closes against a tooth-like process

Chelicera (plural chelicerae): One of two appendages at the front of the carapace, made up of basal portion, the paturon, and the fang; sometimes called the jaw; see also Chelicerae

Cheliceral furrow: A shallow groove on the basal portion of a chelicera accommodating the fang, usually having teeth on its margins

Cheliceral tooth: A tooth-like extension on the margin of the cheliceral furrow

Chilum: A small hardened plate (sclerite) at the base of the chelicerae, under the clypeus

Claw → tarsal claw

Claw tuft: A dense group of hairs or bristles (setae) underneath the paired tarsal claws, usually well developed in hunting spiders

Clypeus: The area of the carapace between the anterior (frontmost) eyes and the anterior edge of the carapace

Colulus: A short protuberance in the middle of the underside of the abdomen in front of the spinnerets, considered to be a modification of the cribellum

Conductor → palpal bulb

Copulatory opening: An opening in the ventral abdomen of female spiders; in entelegyne spiders, a double opening in the epigyne through which the embolus is inserted; in haplogyne spiders, a single opening through which male palpal bulb is inserted

Coxa → segments

Crenulate: Having longitudinal ridges

Cribellum: A sieve-like plate in front of the spinnerets, used in conjunction with the calamistrum; spiders with a cribellum are called cribellate, those without ecribellate; see also Cribellum

Cymbium (plural cymbia): The end part of the tarsus of the pedipalp in a mature male, usually hollowed out and bearing the palpal bulb

D
Dionychous: With two claws on the tarsus of each leg; a feature of spiders in the clade Dionycha

Dorsal groove → fovea

Dorsum: The upper (dorsal) portion or surface of the body or abdomen; the adjective dorsal may be applied to the upper portion or surface of any part of the body; → ventrum

E
Ecribellate → cribellum

Embolus → palpal bulb

Endite → maxilla

Endosternite: An internal hardened plate (sclerite)

Entelegyne: A spider whose female has an epigyne and separate ducts leading to spermathecae for sperm storage and to the uterus for fertilization, creating a "flow-through" system; → haplogyne; see also Entelegynae

Epigastric furrow or epigastric fold: A transverse slit towards the front (anterior) of underside of the abdomen; the front pair of book lungs open at the edge of this furrow as do the genital openings (gonopores)

Epigyne or epigynum (plural epigynes): A hardened plate on the underside of the female abdomen in which the copulatory openings are located; only fully developed in mature females of entelegyne spiders; see also Epigyne

Eyes: The basic number of eyes is eight, arranged in two rows (e.g. as in Gnaphosidae); the front row are the anterior eyes, the row behind the posterior eyes; the four eyes to the edges are the lateral eyes, the four eyes in the centre the median eyes; the number of eyes, their sizes and arrangement varies widely and is characteristic of spider families  → main eye, secondary eye

F
Fang: The final hinged part of the chelicera, normally folded down into a groove in the basal part of the chelicera; venom is injected via an opening near the tip of the fang

Femur → segments

Fertilization duct: A duct in female entelegyne spiders leading from the spermathecae to the uterus

Folium: A broad leaf-like marking along the medial line of the top of the abdomen

Fovea (also called thoracic furrow or dorsal groove): A depression or pit in the centre of the carapace of a spider marking an inward projection of the exoskeleton to which stomach muscles are attached

G
Genital opening → gonopore

Gnathocoxa → maxilla

Gonopore: The genital opening; located in the epigastric furrow; the opening of the duct from the uterus in females and from the testes in males; see also Gonopore

H
Haematodocha → palpal bulb

Haplogyne: A spider whose female lacks an epigyne and in which the same ducts are used to transport sperm to the uterus and to the spermathecae; → entelegyne

Heart mark: A narrow marking along the top of the abdomen roughly corresponding to the location of the heart

L
Labio-sternum mound: A mound separating the  labium from the sternum, found in found in some tarantulas, where it can be a diagnostic feature

Labium (plural labia): A hardened plate (sclerite) between the maxillae at the front of the sternum; see also Arthropod mouthparts: Labium

Labrum (plural labra): A component (the "upper lip") of the mouthparts, concealed by the chelicerae; see also Arthropod mouthparts: Labrum

Lateral (applied to appendages): Viewed from above or below, the sides of the leg or pedipalp, i.e. the surfaces parallel to the line of sight; → prolateral, retrolateral

Laterigrade: With legs directed to the side, hence appearing like and moving like a crab; → prograde

leg formula: The legs are numbered from the front from I to IV; the relative length of the legs can be represented by four numbers from the longest to the shortest; e.g. 1423 = first leg (leg I) is longest and third leg (leg III) is shortest

M
Main eye: One of the two anterior median eyes (AME) that have the light-detecting units (rhabdomeres) pointing towards the source; particularly enlarged in the families Salticidae and Thomisidae; → secondary eye, eyes

Mastidion (plural mastidia): A projection or bump on the chelicerae (not to be confused with teeth)

Maxilla (also called endite or gnathocoxa): Modified coxa of the pedipalp, used in feeding; not the structure called by this name in other arthropods, for which see Maxilla (arthropod mouthpart)

Metatarsus → segments

O
Operculum or branchial operculum (plural opercula): One of the plates on the ventral surface of the abdomen, just in front of the epigastric furrow, covering the book lungs, often pale, yellow or orange in colour; two pairs in Mygalomorphae, one pair in other spiders

Opisthosoma → abdomen

P
Palp → pedipalp

Palpal bulb (also called bulbus, palpal organ, genital bulb): The copulatory organ of the male spider, carried on the modified last segment of the pedipalp, used to transfer sperm to the female; see also Palpal bulb

Conductor: A part of the palpal bulb that accompanies and supports the embolus

Embolus: The final part of the palpal bulb containing the end of the sperm duct, usually thin, sharp-tipped and strongly hardened (sclerotized)

Haematodocha (plural haematodochae): A membranous, inflatable part of the palpal bulb

Median apophysis: A projection (apophysis) of the palpal bulb, below the conductor

Subtegulum: A hardened part of the palpal bulb nearer its base than the tegulum

Tegulum: The main hardened part of the palpal bulb

Paracymbium: An outgrowth of the cymbium on the male pedipalp

Patella → segments

Paturon: The basal segment of a chelicera to which the fang connects

Pedicel or pedicel: The narrow connection between the cephalothorax and abdomen

Pedipalp (plural pedipalps or pedipalpi; also called just palp): The second appendage of the cephalothorax in front of the first leg; bears the palpal bulb in male spiders; → segments

Plumose setae are hairs having outgrowths or appendages on two sides, giving a feather-like appearance; the appendages vary in number, size and arrangement

Pluridentate: Having multiple teeth

Procurved: Used to describe a structure which is curved in such a way that the outer edges are in front of the central part; opposite recurved

Prolateral: Viewed from above or below, the side of a leg or pedipalp nearest the mouth, i.e. the side facing forward; opposite retrolateral (includes diagram)

Promarginal: The side of the cheliceral furrow facing forward; particularly used for describing teeth; opposite retromarginal

Prosoma → cephalothorax

R
Rastellum (plural rastella): An often rake-like structure at end of the chelicera in mygalomorph spiders; used in burrowing

Rebordered: Having a thickened edge (i.e. border) (more rarely seen as reborded, from the French , e.g. in Levy (1984)); particularly used of the labium

Receptaculum (plural receptacula) → spermatheca

Recurved: Used to describe a structure which is curved in such a way that the outer edges are behind the central part; opposite procurved

Retrolateral: Viewed from above or below, the side of a leg or pedipalp furthest from the mouth, i.e. the side facing backwards; opposite prolateral

Retrolateral tibial apophysis: A backward-facing projection on the tibia of the male pedipalp; distinguishing feature of the RTA clade

Retromarginal: The side of the cheliceral furrow facing backward (towards the posterior end of the spider); particularly used for describing teeth; opposite promarginal

S
Sclerite: A single hardened (sclerotized) part of the external covering (tegument, exoskeleton)

Scopula (plural scopulae): A brush of hairs (setae); called a claw tuft when on the end of the foot (tarsus), where it improves adhesion

Scutum (plural scuta): A hardened (sclerotized) plate on the abdomen of some spiders

Secondary eye: An eye belonging to the three pairs – anterior lateral eyes (ALE), posterior median eyes (PME) and posterior lateral eyes (PLE) – that are primarily movement detectors and have the light-detecting units (rhabdomeres) pointing away from the source; → main eye, eyes

Segments or articles of the legs and pedipalps:

Coxa (plural coxae): First leg segment, between body and trochanter; the coxa of the pedipalp is heavily modified to form the maxilla or endite

Trochanter: Second leg segment, between coxa and femur

Femur (plural femora): Third leg segment, between trochanter and tibia

Patella (plural patellae): Fourth leg segment, between femur and tibia

Tibia (plural tibiae): Fifth leg segment, between patella and metatarsus

Metatarsus (plural metatarsi; also called basitarsus): Sixth leg segment, between tibia and tarsus; absent in the pedipalp

Tarsus (plural tarsi; also called telotarsus): Seventh (last) leg segment, after the metatarsus

Seta (plural setae): A bristle; spiders have a variety of hair-like structures of increasing size that are referred to as hairs, bristles (setae) or spines

Sigillum  (plural sigilla): A circular indentation on the outside of the spider, showing where an internal muscle is attached; particularly on the sternum in some Mygalomorphae and on the dorsum in some Araneomorphae

Sperm duct: A duct in the male palpal bulb used to store sperm

Spermatheca (plural spermathecae; also called receptulacum, receptulacum seminis): A structure in the abdomen of female spiders used to store sperm after insemination and before fertilization; see also Spermatheca

Spigot: A small pointed or cylindrical structure at the tip of a spinneret from which silk emerges

Spine: A pointed, rigid structure on body and legs, usually with a basal joint; spiders have a variety of hair-like structures of increasing size that are referred to as hairs, bristles (setae) or spines

Spinneret: An appendage borne on the abdomen, typically one of six arranged in three pairs: anterior (anterior median, AMS), median (posterior median, PMS) and posterior (posterior lateral, PLS); silk emerges from small spigots on the spinnerets; see also Spinneret

Sternum: The lower (ventral) portion of the cephalothorax

Stridulating organ: A series of thin ridges on a hardened part of the body; rubbing this with a matching series of short, stiff bristles (setae) elsewhere on the body creates a sound

Subtegulum → palpal bulb

T
Tapetum (plural tapeta): A light-reflecting layer in a secondary eye making the eye appear pale

Tarsal claw (claw): One of a set of claws at the tip of the tarsus; there may be a single pair, often concealed in a claw tuft, or an additional third central claw, much smaller than the other two

Tarsus → segments

Teeth: Pointed growths or bumps along the margins of the cheliceral furrow

Tegulum → palpal bulb

Thoracic furrow → fovea

Tibia → segments

Trachea (plural tracheae): A thin hardened internal tube, part of the respiratory system in many araneomorph spiders; opens on the underside of the abdomen via a tracheal spiracle; see Trachea § Invertebrates

Trichobothrium (plural trichobothria): A slender hair-like structure of variable length on the legs and pedipalps, arising from a special socket; used to detect air movements, including sounds; → seta, spine

Trochanter → segments

U
Unidentate: Having a single tooth

V
Venter (or ventrum): The lower (ventral) portion or surface of the body or abdomen; the adjective ventral may be applied to the upper portion or surface of any part of the body; → dorsum

Abbreviations
Some abbreviations commonly found in descriptions of spider anatomy include:

ALE: anterior lateral eyes → eyes
ALS: anterior lateral spinnerets → spinneret
AME: anterior median eyes → eyes
DTA: dorsal tegular apophysis, apophysis on the back of the tegulum 
DTiA: dorsal tibial apophysis, apophysis on the back of a tibia 
LTA: lateral tegular apophysis, apophysis on the side of the tegulum 
MOQ: median ocular quadrangle, the quadrangle formed by the four median eyes, → eyes
PLE: posterior lateral eyes →  eyes
PLS: posterior lateral spinnerets → spinneret
PME: posterior median eyes →  eyes
PMS: posterior median spinnerets → spinneret
RCF: retrolateral cymbial fold, fold on the retrolateral surface of the cymbium
RTA: retrolateral tibial apophysis, apophysis on the retrolateral surface of a tibia
VTA: ventral tegular apophysis, apophysis on the underside of the tegulum 
VTiA: ventral tibial apophysis, apophysis on the lower surface of a tibia

See also
 Spider anatomy
 Glossary of entomology terms
 Anatomical terms of location

References

Bibliography
 
 
 
 
 
 

 
Spider terms