Right now, I have 18, 13 cup Glad containers with numerous tiny Pipevine Swallowtails in them. I've been placing a 5 oz. cup in the center and drapping over a piece of papertowel. Then I add the leaves. Some of the leaves are so large that I have to fold them. This design keeps the frass (butterfly poop) off the leaves and off the caterpillars. The top of the 13 cup Glad container has many holes that I stuck with a corn holder. The corn holder makes some nice round holes that are too small for the tiny larvae to escape, but large enough to keep the moisture level down.
Tomorrow, I will probably need to buy some more container and divide them. I usually don't raise more than 9 caterpillars in a container. It is just too crowded for them.
If I left these caterpillars outside, the European paperwasp would be carving them up for breakfast, lunch, and dinner. It is amazing how many more butterflies that are in my yard since I started trying to get rid of this wasp. They must be eating a ton of caterpillars.