Keelbug

The Keelbug is a deleted Covenant race seen in the Halo 2 Collector's Edition Video. It was supposed to come into the battlefield, cut dead bodies into sections, and then fly off with them, as a way of cleaning up the bodies.

The concept of an insect-like creature as an enemy may have led to the design of the Drone that appears in Halo 2 and Halo 3.