Glossary of arachnology terms

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This glossary describes the terms used in the formal descriptions of arachnids, particularly spiders.


  • Apophysis: a process or outgrowth of the exoskeleton from any part of the body, but particularly on the appendages

Head and body[edit]

  • Abdomen or opisthosoma: One of two body segments, towards the posterior end.
  • Carapace: The upper (dorsal) portion of the cephalothorax.
  • Cephalothorax or prosoma: One of two body segments, towards the anterior end.
  • Chelicera: The appendage that includes the fang. (Sometimes called the jaw.)
  • Clypeus: the area of the carapace between the anterior eyes and the anterior edge of the carapace.
  • Dorsum: The upper (dorsal) portion of the body or abdomen.
  • Dorsal groove: Another name for the fovea of the carapace.[1]
  • 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.[2]
  • Labio-sternum mound: A mound separating the labium from the sternum, found in found in some tarantulas, where it can be a diagnostic feature.[3]
  • Sternum: The lower (ventral) portion of the cephalothorax.
  • Thoracic furrow: Another name for the fovea of the carapace.[4]
  • Venter (or ventrum): The lower (ventral) portion of the body or abdomen.

Legs and palps[edit]

  • Segments:
    • Coxa : first leg segment, between body and trochanter.
    • Trochanter : second leg segment, between coxa and femur
    • Femur : third leg segment, between trochanter and tibia.
    • Patella: fourth leg segment, between femur and tibia.
    • Tibia : fifth leg segment, between patella and metatarsus.
    • Metatarsus (or basitarsus): sixth leg segment, between tibia and tarsus; absent in the pedipalp.
    • Tarsus (or telotarsus): seventh (last) leg segment, after the metatarsus.
  • Lateral (applied to legs): viewed from above or below, the sides of the leg or palp, i.e. the surfaces parallel to the line of sight
  • Prolateral: viewed from above or below, the side of the leg or palp nearest the mouth, i.e. the side facing forward
  • Retrolateral: viewed from above or below, the side of the leg or palp furthest from the mouth, i.e. the side facing backwards


  • Maxilla: modified coxa of the pedipalp, used in feeding.
  • Carpoblem: the principal tibial apophysis on the male pedipalp. (Typically, this is just called the tibial apophysis.)
  • Retrolateral tibial apophysis: a backward-facing projection on the tibia of the male pedipalp.


Larinioides cornutus spider showing folium on abdomen
  • Folium : A broad leaf-like marking along the medial line of the top of the abdomen.
  • Heart mark : A narrow marking along the top of the abdomen roughly corresponding to the location of the heart.


Some abbreviations commonly found in descriptions of spider anatomy include:[citation needed]

  • ALE: anterior lateral eyes
  • ALS: anterior lateral spinnerets
  • AME: anterior median eyes
  • DTA: dorsal tegular apophysis
  • DTiA: dorsal tibial apophysis
  • LTA: lateral tegular apophysis
  • MOQ: median ocular quadrangle
  • PLE: posterior lateral eyes
  • PLS: posterior lateral spinnerets
  • PME: posterior median eyes
  • PMS: posterior median spinnerets
  • RCF: retrolateral cymbial fold
  • RTA: retrolateral tibial apophysis
  • VTA: ventral tegular apophysis
  • VTiA: ventral tibial apophysis

See also[edit]


  1. ^ Foelix 2011, p. 17.
  2. ^ Roberts 1995, pp. 13–14.
  3. ^ Smith, A. M. (1990). Baboon spiders: Tarantulas of Africa and the Middle East. Fitzgerald Publishing, London, pp. 1-142
  4. ^ Foelix 2011, p. 18.


  • Foelix, Rainer F. (2011). Biology of Spiders (3rd p/b ed.). Oxford University Press. ISBN 978-0-19-973482-5. 
  • Comstock, John Henry (1920) [First published 1912]. The Spider Book. Doubleday, Page & Company. 
  • Roberts, Michael J. (1995). Spiders of Britain & Northern Europe. London: HarperCollins. ISBN 978-0-00-219981-0.