In the episode, the worms cannot survive outside the "fog", which is first shown when Nick and Stephen trap the mouthparts in a door separating the fog: if separated from their natural atmosphere, oxygen, highly poisonous to them, kills them. The fog is the Pre-Cambrian atmosphere, which presumably comes through the anomaly. When they are faced with an increase of heat, they explode to spawn their young which then attempt to burrow into a living host. They can also spit a brown-coloured slime, which might be used to track or even attack their prey. It also reappears in a classroom during the convergence of the anomalies in Series 5. Abby and Becker shot them with their EMDs. It is unknown what happened to them, but although they were sent to captured them and it is likely that they were kept in the ARC, but this is very difficult as these worms would be killed from the lack of Precamberian fog.
- It has been speculated that the real life prehistoric worm Ottoia is the young of the Precambrian Worms in the Primeverse. But this is unlikely as Ottoia was an aquatic lifeform, while the Worms appear to be lifeforms that live on land.