Moth
From Halopedia, the Halo wiki
Moths are a type of insect that are typically nocturnal. They navigate at night using the light of the moon, which causes their well-known behavior of crowding around lights at night.
They are seen in the swamps of the level 343 Guilty Spark in Halo: Combat Evolved. They, along with the Sea Worms on the Silent Cartographer, are the only known species of Installation 04. The calls of various other creatures are heard at certain points throughout the game, but they are of unknown species. These sounds are presumably from owl-like birds and crickets. In Halo: Combat Evolved, the moths are harmless to the Covenant and humans alike.