Orbicular

Definition

Having a circular, disc-like, or ring-shaped form; approximately round in outline. In arthropod morphology, describes body regions, markings, sclerites, or other structures that are circular or nearly so when viewed from above, as opposed to elongate, triangular, or irregular shapes.

Etymology

Latin orbiculus, diminutive of orbis 'circle, disk'

Example

The orbicular spot on the forewing of many Noctuidae moths is a circular or ocellate marking used in species identification; similarly, the orbicular sclerite in some spider abdomens forms a distinct disc-like plate.

Synonyms

• circular
• discoid
• round
• annular

Related Terms

• ocellate
• discoid
• Reniform
• Clavate
• orb
• maculation

Usage Notes

Distinguished from 'reniform' (kidney-shaped) and 'clavate' (club-shaped) in lepidopteran wing pattern terminology. In arachnology, 'orbicular' may describe the overall body shape of certain crab spiders (Thomisidae) or the form of abdominal sclerites. Not to be confused with 'orbiculate,' which emphasizes a flattened disc shape. The term implies two-dimensional circularity rather than spherical form; for three-dimensional roundness, 'globose' or 'spherical' is preferred.