Although it sounds strange, keeping pillbugs in a sealed terrarium or glass jar is sometimes popular with children as an experiment in observing natural ecology. These are utterly harmless creatures, and it can be instructive to watch the manner in which nature breaks down dead material. All that's required is to provide the bugs with a regular diet of moist paper, wood chips, or compost layered over some ordinary soil. Make sure the container is well-ventilated, as these creatures need air to thrive.