ommatidia's Usage Examples:

like the single elements (ommatidia) of a compound insect eye, in others like simple ocelli.

Watase has shown, in a very convincing way, how by deepening the pit-like set of cells beneath a simple lens the more complex ommatidia of the compound eyes of Crustacea and Hexapoda may be derived from such a condition as that presented in the lateral eyes of Limulus and Scorpio.

- Section through a portion of the lateral eye of Limulus, showing three ommatidia - A, B and C.

In the specialized ommatidia of the compound eyes of Crustacea and Hexapods the rhabdom is an important structure.

In Crustacea and Hexapoda of all grades we find compound eyes with the more complicated ommatidia described above.

They consist of a varying number of ommatidia or visual elements, covered by a transparent region of the external cuticle forming the cornea.

The compound eye of the king-crab (Limulus) is the only recognized instance of ommatidia in their simplest state.

In most cases this cornea is divided into lenticular facets corresponding to the underlying ommatidia.

'There are over 25,000 ommatidia in the eye of a hawk moth.