Määritelmä: A class of complex shallow wetlands in central, southern and eastern Africa, particularly in Zambia and Zimbabwe. They are generally found in higher rainfall flat plateau areas, and have river-like branching forms which may be nowhere very large, but common enough to add up to a large area.
Määritelmä: superposition compound eyes where each ommatidium is equipped with a lens cylinder arrangement, producing the equivalent of a pair of lenses, with the first lens producing a small image halfway down the structure and the second lens turning the image back into a parallel beam. In the process the ray direction is reversed. Thus, the emerging beam is on the same side of the axis as the entering beam—the condition for obtaining a superposition image from the whole array.
