From Halopedia, the Halo wiki

A fan-made image of Mister Chief created for use in Template:Realworld.
This article contains information about a non-canonical subject that, while official, is not part of the established Halo universe.
A sketch of the Keelbug

The Keelbug is a deleted Covenant species seen in the Halo 2 Collector's Edition Video. It was supposed to come into the battlefield, cut up dead bodies into sections, and then fly off with them, as a way of cleaning up the bodies. They were originally going to be used in Halo: Combat Evolved as a clever method of removing NPC corpses to free up memory. This race would have been a gruesome addition to the Covenant.

The concept of an insect-like creature as an enemy may have led to the design of the Yanme'e that later first appears in Halo 2.

The keelbug is mentioned in the description of the Bleached Bone armor coating for Halo Infinite.