Glossary of arachnology terms

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

Terms

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

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]
Sternum: The lower (ventral) portion of the cephalothorax.
Thoracic furrow: Another name for the fovea of the carapace.^[3]
Venter (or ventrum): The lower (ventral) portion of the body or abdomen.

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.
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 (the inside surface of the palp)
Retrolateral: viewed from above or below, the side of the leg or palp furthest from the mouth (the outside surface of the palp)

Carpoblem: the principal tibial apophysis on the male pedipalp. (Typically, this is just called the tibial apophysis.)

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]}

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