elytron
An elytron (plural: elytra) is a modified, hardened forewing of certain insects, commonly seen on beetles. The elytra primarily serve as protective wing-cases for the hindwings underneath, which are used for flying. To fly, a beetle typically opens the elytra and then extends their wings, flying while still holding the elytra open, though some beetles can fly with the elytra closed. In some species, the elytra are fused together, rendering the insect flightless.