compound eye (oculus)

compound eye(s) - the two large many-faceted eyes placed on each side of the head of insects (and some other arthropods), besides which they may also possess simple eyes (ocelli). Compound eyes consist of numerous hexagonal facets, the lenses of which combine the characters of both crystalline and vitreous humours. The individual visual elements are called ommatidia (singular ommatidium). Compound eyes are sometimes called oculi (singular oculus), or simply, eyes. The compound eyes are particularly prominent in certain Diptera (flies) and Odonata (dragonflies and damselflies).