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.

Links within the glossary are shown in this style.

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

Apodeme: see sigillum

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: see 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: see operculum

Bulbus: see 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): see 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 or caput: 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: see 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: see palpal bulb

Copulatory duct: An internal tube (duct) from the copulatory opening 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 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: see 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 ("wart") on the endites and labium of Mygalomorphae

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: see 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; see ventrum

E

Ecribellate: see cribellum

Embolus: see palpal bulb

Endite: see 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; see 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, 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 main eye, secondary eye

F

Falx (plural falces): A dated term for chelicera

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: see 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 (plural fossae): A pit or depression, typically in the epigyne

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: see gonopore

Gnathocoxa: see 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

Gravid: A fertilised female with an enlarged abdomen section right before egg laying has begun.

H

Haematodocha (also spelled hematodocha): see 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; see entelegyne; see also Haplogynae

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 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: see rostrum

Lamella characteristica or just lamella: a sheet-like sclerite on the palpal bulb of many Linyphiidae species

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; see prolateral, retrolateral

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

Leg parts or segments: see segments

Lorum: A set of sclerites covering the dorsal surface of the pedicel.

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 secondary eye, eyes

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

Maxilla (plural maxillae; 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: see segments

O

Ocular area or ocular quadrangle: The area of the carapace which includes the eyes.

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: see abdomen

P

Palp: see 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: see segments

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

Pedicel or petiolus: 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; see segments, see also Pedipalp

Plumose: Used to describe hairs (setae) having outgrowths or appendages on two sides, giving a feather-like appearance; the appendages vary in number, size and arrangement

Pluridentate: Having multiple teeth

Postembryo (also called larva): The stage of development between hatching from the egg and first molting

Preening brush: a dense cluster of setae near the ventral tip of the posterior metatarsi; 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 recurved

Prolateral: Viewed from above or below, the side of a leg or pedipalp nearest the mouth, i.e.