I know a guy who used egg crates. THey havbe those little bumpy things that the eggs sit in and each of those can be cut out of some of the deeper egg cartons and used as a housing for smaller spiderlings. He used cling film with small holes poked in it on the top of each one to keep it inside. These can be picked up for free at any grocery store that has bulk flats of eggs. I have millions of these cartons that I got from a major Canadian grocer to soundproof a room.