Structural specialization in the dorsal retina of the bee, Apis mellifera.

Electron microscopic investigations on the eye of the worker bee showed that the ommatidia located in the uppermost part of the dorsal half of the eye are characterized by a distinct structural specialization: Nine visual cells contribute microvilli to the rhabdom over its full length. Within these rhabdoms the microvilli are arranged in at least three different directions. This specialization affects an area of at least 60 ommatidia. The most dorsal eye region differs, therefore, structurally from all other regions which have been investigated to date. Because the ommatidia in question are oriented skyward, their peculiar structure is discussed with respect to several concepts of polarized light detection by the bee.