Albert Barnes 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)

Scorpions - By this word, some understand whips having leaden balls at the ends of their lashes with hooks projecting from them; others, the thorny stem of the eggplant, or “the scorpion plant.” But it seems best to regard the expression as a figure of speech.