Glossary of spider terms
Accessory claw: Modified at the tip of the in web-building spiders; used with to grip strands of the web
Apophysis (plural apophyses): An outgrowth or process changing the general shape of a body part, particularly the appendages; often used in describing the male  →
Bidentate: Having two 
Calamistrum (plural calamistra): Modified setae (bristles) on the of the fourth leg of spiders with a , arranged in one or more rows or in an oval shape, used to comb silk produced by the cribellum; see also Calamistrum
Cephalic region or caput: The front part of the , separated from the thoracic region by the 
Cephalothorax or prosoma: One of the two main body parts (tagmata), located towards the anterior end, composed of the head ( or caput) and the thorax (thoracic region), the two regions being separated by the ; covered by the and bearing the , legs, and mouthparts
Cervical groove: A shallow U-shaped groove, separating the and thoracic regions of the 
Chelate: A description of a where the closes against a tooth-like process
Cheliceral furrow: A shallow groove on the basal portion of a accommodating the , usually having on its margins
Cheliceral tooth: A tooth-like extension on the margin of the 
Chilum: A small hardened plate (sclerite) at the base of the , under the 
Claw tuft: A dense group of hairs or bristles (setae) underneath the paired , usually well developed in hunting spiders
Clypeus: The area of the between the anterior (frontmost) and the anterior edge of the carapace
Colulus: A short protuberance in the middle of the underside of the in front of the , considered to be a modification of the 
Copulatory opening: An opening in the ventral of female spiders; in entelegyne spiders, a double opening in the through which the is inserted; in haplogyne spiders, a single opening through which male is inserted
Crenulate: Having longitudinal ridges
Cymbium (plural cymbia): The end part of the of the in a mature male, usually hollowed out and bearing the 
Endosternite: An internal hardened plate (sclerite)
Epigastric furrow or epigastric fold: A transverse slit towards the front (anterior) of underside of the ; the front pair of open at the edge of this furrow as do the genital openings ()
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 → ,
Fang: The final hinged part of the , 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
Fertilization duct: A duct in female spiders leading from the to the uterus
Fossa (plural fossae): A pit or depression, typically in the 
Fovea (also called thoracic furrow or dorsal groove): A depression or pit in the centre of the of a spider marking an inward projection of the exoskeleton to which stomach muscles are attached
Laterigrade: With legs directed to the side, hence appearing like and moving like a crab; →
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
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; → ,
Operculum or branchial operculum (plural opercula): One of the plates on the surface of the , just in front of the , covering the , often pale, yellow or orange in colour; two pairs in Mygalomorphae, one pair in other spiders
Palpal bulb (also called bulbus, palpal organ, genital bulb): The copulatory organ of the male spider, carried on the modified last segment of the , 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 on the male 
Paturon: The basal segment of a to which the connects
Pedicel or pedicel: The narrow connection between the and 
Pedipalp (plural pedipalps or pedipalpi; also called just palp): The second appendage of the in front of the first leg; bears the in male spiders; →
Plumose: Used to describe hairs () having outgrowths or appendages on two sides, giving a feather-like appearance; the appendages vary in number, size and arrangement
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: Used to describe a structure which is curved in such a way that the outer edges are behind the central part; opposite
Retrolateral tibial apophysis: A backward-facing projection on the tibia of the male ; distinguishing feature of the RTA clade
Scape: An elongated process or appendage of some 
Sclerite: A single hardened (sclerotized) part of the external covering (tegument, exoskeleton)
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; → ,
- Coxa (plural coxae): First leg segment, between body and trochanter; the coxa of the is heavily modified to form the 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
- Tarsus (plural tarsi; also called telotarsus): Seventh (last) leg segment, after the metatarsus
Sigillum (plural sigilla): A circular indentation on the outside of the spider, showing where an internal muscle is attached; particularly on the in some Mygalomorphae and on the in some Araneomorphae
Sperm duct: A duct in the male used to store sperm
Spermatheca (plural spermathecae; also called receptulacum, receptulacum seminis): A structure in the 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 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 , 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 on the spinnerets; see also Spinneret
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
Tapetum (plural tapeta): A light-reflecting layer in a making the eye appear pale
Tarsal claw (claw): One of a set of claws at the tip of the ; there may be a single pair, often concealed in a , or an additional third central claw, much smaller than the other two
Trachea (plural tracheae): A thin hardened internal tube, part of the respiratory system in many araneomorph spiders; opens on the underside of the via a tracheal spiracle; see Trachea § Invertebrates
Trichobothrium (plural trichobothria): A slender hair-like structure of variable length on the legs and , arising from a special socket; used to detect air movements, including sounds; → ,
Unidentate: Having a single tooth
Some abbreviations commonly found in descriptions of spider anatomy include:
- ALE: anterior lateral eyes →
- ALS: anterior lateral spinnerets →
- AME: anterior median eyes →
- DTA: dorsal tegular apophysis, on the back of the
- DTiA: dorsal tibial apophysis, on the back of a
- LTA: lateral tegular apophysis, apophysis on the side of the
- MOQ: median ocular quadrangle, the quadrangle formed by the four median eyes, →
- PLE: posterior lateral eyes →
- PLS: posterior lateral spinnerets →
- PME: posterior median eyes →
- PMS: posterior median spinnerets →
- RCF: retrolateral cymbial fold, fold on the surface of the
- RTA: retrolateral tibial apophysis, on the surface of a
- VTA: ventral tegular apophysis, on the underside of the
- VTiA: ventral tibial apophysis, on the lower surface of a
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