The container I use more of is about 3 cup size. I place a small piece of paper towel in the bottom to aid in cleaning up frass (poop). I put the foam upside down in a shallow bowl of water and then when wet, insert the host plant sprigs, including the cats that are feeding on them.
My lids are the most important thing for a successful project. The cloth is simular to the inside liner in swimwear, tricot I think is it's name. The center of the lid is removed and a piece of the mesh hot glued at the corner of the under side (careful to keep it out of the seal). The fabric has an tight weave and doesn't ravel. The microscopic predators can't access the caterpillars, and also if it is used for holding chrysalis and one has been parasitised, they can't get out into your garden.
