labrum
1. In Echinozoa, a lip-like projection of the peristome.

2. A broad piece of cuticle which forms the upper ‘lip’ in an insect. The labrum articulates with the clypeus. It is anterior to the mandibles, and can be moved away from them by a pair of muscles, or closed down on to them by another pair of muscles with a rocker-like action.

labrum The upper lip in the mouthparts of an insect. It is formed from a plate of cuticle hinged to the head above the mouth and is used in feeding.

labrum (lay-brŭm) n. (pl. labra) a lip or liplike structure; occurring, for example, around the margins of the acetabulum.