Scrub grub

Scrub Grubs are anxious creatures with hairs that cover their turgid bodies. These hairs are always in motion, sensing for danger. They are a small species that inhabit at least one Covenant world. They tend to board space ships and feed on the machinery. On long space flights, their numbers have to be contained in order to prevent them from damaging any vital systems.

Scrub Grubs are a type of arthropod, like the Yanme'e, though far smaller and non-sentient.

They are likely to be the equivalent of rats found on the Human homeworld Earth.

Trivia
=Sources=
 * Grunts often use these for sporting games during space travel.