Charles Ellicott Commentary 1 Kings 12:11

"And now whereas my father did lade you with a heavy yoke, I will add to your yoke: my father chastised you with whips, but I will chastise you with scorpions." — 1 Kings 12:11 (ASV)

The scorpion is probably (like the Roman fiagellum) a whip, the lash of which is loaded with weights and sharp points.