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 . 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 Apophysis (plural apophyses): An outgrowth or process changing the general shape of a  body part, particularly the appendages; often used in describing the male → 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 → Bulbus → 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) → 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 → 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 → 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 → 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 → 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; → E. Ecribellate → Embolus → Endite → 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 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 → , F. 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 → 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 → Gnathocoxa → 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 → 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 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 (plural labra): A component (the "upper lip") of the mouthparts, concealed by the ; see also Arthropod mouthparts: Labrum 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; → , 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 Leg parts or segments → 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; → , Mastidion (plural mastidia): A projection or bump on the chelicerae (not to be  confused with ) Maxilla (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 → O. 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 → P. Palp → 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 Paracymbium: An outgrowth of the on the male Patella → 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 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 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 → 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) → 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 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; → , Segments or articles of the legs and : 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 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 Sternum: The lower (ventral) portion of the 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 → T. 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 Tarsal organ: a small pit, usually spherical and on the surface of each , believed to respond to humidity Tarsus → Teeth: Pointed growths or bumps along the margins of the Tegulum → Thoracic furrow → Tibia  → 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; → , Trochanter → U. Unidentate: Having a single tooth V. Venter (or ventrum): The lower (ventral) portion or surface of the body or ; the adjective ventral may be applied to the lower portion or surface of any part of the body; →  Abbreviations. Some abbreviations commonly found in descriptions of spider anatomy include: