Ocellus
Description:
(plural: ocelli). A "simple eye". A small photosensitive structure, consisting of a single ommatidium (= facet). When present, ants have three ocelli grouped in a triangle on the central portion of the vertex, with one median ocellus (= anterior ocellus) and two lateral ocelli (= posterior ocelli). Ocelli are usually present in the reproductive caste only.
