The Pegomastax is a very special tame. If u put something in your last hotbar slot it will steal that instead of anything else. So put ca. 100 Mejoberries in your last slot and any Pego under lv 50 will be instant tamed.
They pick-pocket berries and tame themselves. Once tamed, you can carry him on your back.If you get in a sticky situation throw him off your back and he'll attack enemies. I carry him into my base and throw him off my back and he hangs out like a pet. 🥰