tegmen

noun

1. A covering or integument, usually referring to a thin layer or membrane in an organism.
2. An integument such as the inner membrane of the coat of a seed.
3. A covering such as the thin layer of bone in the roof of the middle ear of mammals.
4. In insects such as winged cockroaches and locusts, the stiff, membranous fore wings; in many species they are not primarily used for flight, but serve as protective covering for the delicate hind wings, which are the main organs of flight. The more heavily armoured fore-wings of most beetles are called elytra, not tegmina.