Definission: hearing organ in insects, consisting of a membrane (tympanum) stretched across a frame backed by an air sac and associated sensory neurons
Definission: A thin, almost knife-like, ridge of rock which is typically formed when two glaciers erode parallel U-shaped valleys. The arte is a thin ridge of rock that is left separating the two valleys. Artes can also form when two glacial cirques erode towards one another, although frequently this results in a saddle-shaped pass, called a col.
Definission: Museum National d'Histoire Naturelle (MNHN), Paris, France. URL for main institutional website: http://www.mnhn.fr/museum/foffice/science/science/sommaire.xsp
Definission: 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.
