The scorpions made a reappearance in episode 2.7. One of them was released onto a crowded beach by Oliver Leek to show his power, where it promptly ate two tourists and scared everyone else away. Stephen Hart set out to deal with it on his own, and harpooned it below a bridge. The still alive creature was left to be collected at leisure. Its fate was unknown, but presumably it was killed. However, it's most likely moved to the ARC, since there was no anomaly to send it back to its era.
They appear in a flashback in episode 3.2, when Cutter recognizes the Cleaner and thought he was killed by the scorpions. They are referred to as "Silurian Scorpions" in the episode, but they are listed as "Giant scorpion" on the Primeval official websites.