My biology teacher in high school had a culture of mealworms, and his setup was simple, really. It was a 5 gal bucket, uncovered, filled with sawdust and whatever else he decided for substrate. The mealworms would metamorphose into beetles and to take care of them he just tossed in whatever he had left from lunch (banana peels, orange peels, leftover veggies, etc.). He also tossed in whatever dead animals he had that he wanted to skeletonize (taxidermists and scientists use the beetles to strip carcasses without doing damage to the skeletons). Dermestid beetles (mealworm beetles) will eat anything including other dead beetles/worms so keeping a culture going is the easiest thing in the world.