The Ommatidium
The sides of the cuticular cones are clothed in distal pigment cells. Omnochrome pigments, migrate rapidly toward the base of the cuticle in lighted conditions and form a tight iris cuff around the "pupil" of the cone cells. During the dark, the pigment moves to the base of these epithelial cells and provides the ommatidia with a wider angle of acceptance.
Retinular cells, which are the primary receptor neurons, are grouped like orange slices to make up the ommatidium. In a transverse section (see image below) they create the flower petal shape called the rhabdome.
