ocellus

/oʊˈsɛləs/
noun
  1. A simple eye or an eye-like marking (eyespot) found on certain animals, especially insects and some fish.
    • Many insects have three ocelli on top of their heads that detect light intensity.
    • The ocellus on the wing of a moth can startle a bird into thinking it is a larger animal.
    • Scientists study the ocellus to understand how simple visual systems evolved.
Synonyms