This glossary describes the terms used in formal descriptions of spiders; where applicable these terms are used in describing other arachnids.
Links within the glossary are shown .
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 at the tip of the in web-building spiders; used with to grip strands of the web
Anal tubercle: A small protuberance (tubercule) above the through which the anus opens
Apodeme: see
Apophysis (plural apophyses): An outgrowth or process changing the general shape of a body part, particularly the appendages; often used in describing the male : see
Atrium (plural atria): An internal chamber at the entrance to the in female haplogyne spiders
B Bidentate: Having two
Book lungs: Respiratory organs on the ventral side (underside) of the , in front of the , opening through narrow slits; see also Book lungs
Branchial operculum: see
Bulbus: see
C 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
Caput (plural capita): see
Carapace: A hardened plate (sclerite) covering the upper (dorsal) portion of the ; see also Carapace
Carpoblem: The principal on the male ; also just called the tibial apophysis
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
Chelicera (plural chelicerae): One of two appendages at the front of the , made up of basal portion, the , and the ; sometimes called the jaw; see also Chelicerae
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: see
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
Conductor: see
Copulatory duct: An internal tube (duct) from the through which sperm enters the female; separate from the duct through which fertilized eggs pass in entelegyne spiders
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
Coxa: see
Crenulate: Having longitudinal ridges
Cribellum: A sieve-like plate in front of the , used in conjunction with the ; spiders with a cribellum are called cribellate, those without ecribellate; see also Cribellum
Cuspule: A small spiny outgrowth ("wart") on the and of Mygalomorphae
Cymbium (plural cymbia): The end part of the of the in a mature male, usually hollowed out and bearing the
D Dionychous: With two on the of each leg; a feature of spiders in the clade Dionycha
Dorsal groove: see
Dorsum: The upper (dorsal) portion or surface of the body or ; the adjective dorsal may be applied to the upper portion or surface of any part of the body; see
E Ecribellate: see
Embolus: see
Endite: see
Endosternite: An internal hardened plate (sclerite)
Entelegyne: A spider whose female has an and separate ducts leading to for sperm storage and to the uterus for fertilization, creating a "flow-through" system; see ; see also Entelegynae
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 ()
Epigyne or epigynum (plural epigynes): A hardened plate on the underside of the female in which the are located; only fully developed in mature females of spiders; see also Epigyne
Eyes: The basic number of eyes is eight, typically 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 anterior median eyes are called the main eyes or direct eyes, while the other eyes are called the secondary eyes or indirect eyes; the number of eyes, their sizes and arrangement varies widely and is characteristic of spider families; see ,
F Falx (plural falces): A dated term for
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
Femur: see
Fertilization duct: A duct in female spiders leading from the to the uterus
Folium: A broad leaf-like marking along the medial line of the top of the
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
G Genital opening: see
Gnathocoxa: see
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
Gravid: A fertilised female with an enlarged abdomen section right before egg laying has begun.
H Haematodocha (also spelled hematodocha): see
Haplogyne: A spider whose female lacks an and in which the same ducts are used to transport sperm to the uterus and to the ; see ; see also Haplogynae
Heart mark: A narrow marking along the top of the roughly corresponding to the location of the heart
L Labio-sternum mound: A mound separating the from the , found in some tarantulas, where it can be a diagnostic feature
Labium (plural labia): A hardened plate (sclerite) between the at the front of the ; see also Arthropod mouthparts: Labium
Labrum: see
Lamella characteristica or just lamella: a sheet-like on the of many Linyphiidae species
Lateral (applied to appendages): Viewed from above or below, the sides of the leg or , i.e. the surfaces parallel to the line of sight; see ,
Laterigrade: With legs directed to the side, hence appearing like and moving like a crab; see
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
Leg parts or segments: see
Lorum: A set of covering the dorsal surface of the .
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; see ,
Mastidion (plural mastidia): A projection or bump on the chelicerae (not to be confused with )
Maxilla (plural maxillae; also called endite or gnathocoxa): Modified of the , used in feeding; not the structure called by this name in other arthropods, for which see Maxilla (arthropod mouthpart)
Metatarsus: see
O Ocular area or ocular quadrangle: The area of the which includes the . 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
Opisthosoma: see
P Palp: see
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
Patella: see
Paturon: The basal segment of a to which the connects
Pedicel or petiolus: 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; see , see also Pedipalp
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
Pluridentate: Having multiple
Postembryo (also called larva): The stage of development between hatching from the egg and first molting
Preening brush: a dense cluster of near the tip of the posterior ; called a preening comb when present as a transverse row of setae.
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
Prolateral: Viewed from above or below, the side of a leg or nearest the mouth, i.e. the side facing forward; opposite (includes diagram)
Promarginal: The side of the facing forward; particularly used for describing ; opposite
Prosoma: see
R Rastellum (plural rastella): An often rake-like structure at end of the 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
Receptaculum (plural receptacula): see
Recurved: Used to describe a structure which is curved in such a way that the outer edges are behind the central part; opposite
Retrolateral: Viewed from above or below, the side of a leg or furthest from the mouth, i.e. the side facing backwards; opposite
Retrolateral tibial apophysis: A backward-facing projection on the tibia of the male ; distinguishing feature of the RTA clade
Retromarginal: The side of the facing backward (towards the posterior end of the spider); particularly used for describing ; opposite
Rostrum (also called labrum): A component (the "upper lip") of the mouthparts, concealed by the ; see also Arthropod mouthparts: Labrum
S Scape: An elongated process or appendage of some
Sclerite: A single hardened (sclerotized) part of the external covering (tegument, exoskeleton)
Scopula (plural scopulae): A brush of hairs (setae); called a when on the end of the foot (tarsus), where it improves adhesion
Scutum (plural scuta): A hardened (sclerotized) plate on the 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; see ,
Segments or articles of the legs and :
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 patella
Patella (plural patellae): Fourth leg segment, between femur and tibia