An ocellus (plural: ocelli) is a type of photoreceptor organ in animals. Also called "simple eyes", ocelli are miniature eyes capable just of sensing light but not of distinguishing its direction.

Ocelli are found in many invertebrates. Insects in particular have two types of ocelli: dorsal ocelli are light-sensitive organs on the dorsal surface or on the top of the head. They consist of a few tens of rod cells covered with a corneal lens. Insects with dorsal ocelli also have compound eyes, but lateral ocelli are the only eyes of the larvae of several orders of insects (fleas, springtails, silverfish, and Strepsiptera). Lateral ocelli have a mixture of rod cells and cone cells and are found on the sides of the head, one to six on each side.

External links

• John R. Meyer, Photoreceptors

Eye | Animal anatomy

Ocellus | Ocellus | Medianøye