Maggots (actual name unknown) are parasitic, worm-like creatures encountered by the boy during the Factory section of the game. Maggots, once they have infiltrated a human's brain, take control of their cognitive functions and direct their movements (the purpose of this is unknown, though it is speculated that Maggots do this in order to reach the water to complete their life cycle, as Maggots can be seen floating in water areas by their own, whilst posing no threat to the player). It is also shown that the Maggots dislike the sunlight, and make the person turn around when in the sunrays.
During the boy's encounter with Maggots, he is briefly controlled by one, but quickly kills it by allowing a trio of maggot-eating creatures to grab and eat it from his head using a box for leverage.
Maggots appear to only pose a threat when they are suspended above their victim, as the boy is able to squash them easily underfoot when he walks over the top of them. They also appear to cause no longer term damage to the brain although they apparently burrow past the skull. This could, however, be explained by the boy not actually existing; as he is in Limbo.