Must have chitin in your inventory. They'll walk up to you like a sino and do a little dance making the light behind them green. That's when you walk up to it and feed it a plant z seed or chitin. Plant z seed is preferred food then chitin then mushroom. Plant z seeds tame them instantly. If you do not tame it first time it's light will glow red and then you basically play red light green light. Red light don't move green light feed.