depends on a lot of things, if you were to put them out of water, but in an extremely moist environment (damp moss, etc) they could probably exist for a long time, but if you put them on some sand with a heat lamp, I imagine they would die quite quickly. Are you trying to move them or something? I would suggest that you try to move them as quickly as possible, and ensure that they stay relatively moist (use a spraybottle full of tankwater, maybe?) If you're going to try to keep one in a terrarium for a few weeks or something, don't, it's not a good idea.