Mantises that can be kept communally will still pose a risk of eating each other if they are smaller and not well fed. There will always be a risk to keeping mantises together. All mantis humidity and temperature requirements have a bit of wiggle room for colder/warmer and dryer/wetter conditions; just bear in mind the warmer it is, the quicker your mantis will grow. The opposite is true for cooler temperatures. Most mantises are beginner-friendly, but we will put a note if a mantis is not suitable for beginners.