Scorpions can be found randomly in the open world. You need to deliver them to Bugjiro for the Scorpion Death Ramen side quest. Pay attention to the direction that the scorpion is facing. Just as their stinger/tail is facing you, walk or run up behind them. When the A button icon shows up, quickly press it. If you're not directly behind the scorpion, you'll fail and the scorpion will disappear.