From Halopedia, the Halo wiki
|This article is based on canon information, but the article's name is conjectural, and/or uses descriptions as the title, as there is currently no official name for the subject.|
On the three floors of the city's detention center there are what looks like small, yellow insects crawling around the place. The pests seem to slide on the floor and on the walls, and once anyone approaches one, it slides away. The origin of the pests is unknown, but they may be Scrub Grubs that live onboard Covenant ships and feed on machinery, as they are as abundant as they were said to be.
A number of the pests, as seen in Halo 2.