n. Any of the rods that support each ommatidium in the compound eye of arthropods
the GNU version of the Collaborative International Dictionary of English
n. One of numerous minute rodlike structures formed of two or more cells situated behind the retinulæ in the compound eyes of insects, etc. See Illust. under ommatidium.
The Century Dictionary and Cyclopedia
n. In entomology, a special structure in the eye, consisting of a concrescence of the rods developed on the cells of the retina, when these cells are themselves united in a retinula.