[header] How to keep a pet praying mantis without a cage [title] Buy a potted plant. [step] Since mantises might cannibalize each other, purchase a plant for each one that you intend to keep. Pick a tall plant so they have plenty of room to climb. 
Stick to a small pot, however, so they can find their food at the base more easily. [substeps] Choose a plant with plentiful wide leaves so the mantis has adequate shade to escape the sun.