That’s a great one. I’d say the antlion larva’s sand‑pit trick tops the list. It digs a conical pit in the desert sand, lining the walls with a subtle curve that lets water run down and creates a steep slope. When a bug walks over, it slips and slides straight down the walls, hitting the bottom where the larva is lurking and ready to snap it up. The whole setup takes only a few minutes, but the result is a perfectly engineered trap that turns an ordinary wandering bug into a meal in seconds. It’s a little engineering marvel right there on a tiny scale.