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, 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 above the [|spinnerets] through which the anus opens
Apophysis : 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 : 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 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 : Modified setae 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 : → [|cephalic] region
Carapace: A hardened plate covering the upper 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, located towards the anterior end, composed of the head and the thorax, 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 : 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 at the base of the [|chelicerae], under the clypeus
Claw → tarsal claw
Claw tuft: A dense group of hairs or bristles underneath the paired tarsal claws, usually well developed in hunting spiders
Clypeus: The area of the carapace between the anterior 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
Cuspule: A small spiny outgrowth on the endites and labium of Mygalomorphae
Cymbium : 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 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
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 of underside of the abdomen; the front pair of book lungs open at the edge of this furrow as do the genital openings
Epigyne or epigynum : 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 ; 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
Fossa : A pit or depression, typically in the epigyne
Fovea : 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 : A hardened plate between the maxillae at the front of the sternum; see also Arthropod mouthparts: Labium
Labrum : A component of the mouthparts, concealed by the chelicerae; see also Arthropod mouthparts: Labrum
Lateral : 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 is longest and third leg is shortest

M

Main eye: One of the two anterior median eyes that have the light-detecting units pointing towards the source; particularly enlarged in the families Salticidae and Thomisidae; → secondary eye, eyes
Mastidion : A projection or bump on the chelicerae
Maxilla : Modified coxa of the pedipalp, used in feeding; not the structure called by this name in other arthropods, for which see Maxilla
Metatarsus → segments

O

Operculum or branchial operculum : 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 : 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
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 : 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
Promarginal: The side of the cheliceral furrow facing forward; particularly used for describing teeth; opposite retromarginal
Prosoma → cephalothorax

R

Rastellum : An often rake-like structure at end of the chelicera in mygalomorph spiders; used in burrowing
Rebordered: Having a thickened edge ; particularly used of the labium
Receptaculum → 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 ; particularly used for describing teeth; opposite promarginal

S

Scape: An elongated process or appendage of some epigynes
Sclerite: A single hardened part of the external covering
Scopula : A brush of hairs ; called a claw tuft when on the end of the foot, where it improves adhesion
Scutum : A hardened plate on the abdomen of some spiders
Secondary eye: An eye belonging to the three pairs – anterior lateral eyes, posterior median eyes and posterior lateral eyes – that are primarily movement detectors and have the light-detecting units pointing away from the source; → main eye, eyes
Segments or articles of the legs and pedipalps:
Seta : A bristle; spiders have a variety of hair-like structures of increasing size that are referred to as hairs, bristles or [|spines]
Sigillum : 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 : 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 or spines
Spinneret: An appendage borne on the abdomen, typically one of six arranged in three pairs: anterior, median and posterior ; silk emerges from small spigots on the spinnerets; see also Spinneret
Sternum: The lower 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 elsewhere on the body creates a sound
Subtegulum → palpal bulb

T

Tapetum : A light-reflecting layer in a secondary eye making the eye appear pale
Tarsal 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 : 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 : 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 : The lower 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: