Juvies are a type of small creature found within the Swarm. When a human is taken by a Snatcher, they are placed into a pod. After some time, the human body is transformed into a Juvie. How the process works is unknown, but it is presumed that it forcibly rips apart the human body and remodels it into the Juvie while in the pod as shown when JD discovered a liquified corpse of a captured Gear soldier after cutting open a pod. Fortunately, humans can be freed from the process if they were recently placed in the pods.
Juvies play the role of the scout in the Swarm hierarchy and suppress the enemy using their numbers. They can leap over cover and jump onto walls, making them difficult to target. Juvies can be considered the equivalent of the Wretch. However, they are more dangerous, as they can crawl into special nests to turn into Imagos, who are capable of using weapons. If they mature even further they become Drones.
Juvies can be both chainsawed and retro-charged, both of which are much quicker in comparison to a human-sized enemy.
A "juvie" is a slang term for a juvenile delinquent, or alternatively, a term for an incarceration facility designed for minors. Or for juvenile insects. Alternatively, it can refer to their status as juvenile members of the swarm that have yet to fully mature as Drones.