The lid of their container was ajar, and they can easily climb up the sides. It was a cheap polypropylene tub for insects, and I guess that I didn't close it tightly enough last time I fed them, and the lid popped open at some point. I found one of them in a tub with a different species of newt, which was strange, since I don't know how it could have gotten in there. The other three might have joined it and been eaten by the larger, more aggressive newt, or they could have ventured further afield, in which case they've probably died from dehydration by now and left little mummified corpses behind the furniture somewhere.
