Scrub grub
From Halopedia, the Halo wiki
Scrub grubs are a small species that inhabit at least one Covenant world. They tend to board space ships and feed on the machinery, and are often found on Covenant ships as pests.
Scrub grubs are a type of arthropod, like the Yanme'e, though far smaller and non-sentient.[1] They are anxious creatures with hairs that cover their turgid bodies. These hairs are always in motion, sensing for danger. On long space flights, their numbers have to be contained in order to prevent them from damaging any vital systems. When they are smashed they turn into a mealy liquid. The Unggoy often hunt these creatures for sporting games during space travel.[2]
They are likely to be the equivalent of rats found on the human homeworld Earth.
Trivia
The Covenant pests that can be seen on the level Gravemind in Halo 2 may be scrub grubs.
