ocellular

Ocellular is an adjective used in biology to describe something relating to ocelli, the simple photoreceptive eyes found in a variety of invertebrates, or to organisms that bear such eyes. The term derives from the Latin ocellus, meaning “little eye,” with the suffix -ular to indicate belonging or pertaining to.

In zoological usage, ocelli are light-detecting organs that help with orientation, flight stability, and circadian rhythms, rather than producing detailed images. Many insects possess three ocelli arranged in a triangular pattern on the top of the head in addition to their compound eyes; ocelli are also found in some spiders, crustaceans, and mollusks. Because ocelli are generally not image-forming, ocellular descriptions emphasize presence or configuration rather than visual acuity. The descriptors ocellar, ocellate, and ocellular are used variably across taxa, with ocellar and ocellate more common in some contexts.

The term is mainly encountered in taxonomic and anatomical descriptions. When used, it points to features associated with ocelli—such as their number, arrangement, or the organization of the ocellar system—rather than to broader ocular complexity. For readers seeking related concepts, see ocellus (the simple eye itself), and related adjectives such as ocellar and ocellate.

See also: ocellus, ocellar, ocellate.