Superworms or Zophoba worms are bigger than mealworms but you can order them small. Don't confuse the king mealworm for a zophoba...the kings are hormone grown mealworms and are (in my opinion) a bad choice.
Waxworms (despite how the petstore was keeping them) should not go in the fridge! Room temp is good and take them out of that sawdust.
My waxworms are kept in a couple inches of Honey Bunches of Oats cereal with a few drops of raw honey on top. Waxworms are a beekeepers nightmare...a pest that lives off of honey and honeycomb.
They are very fatty and should be offered sparingly (2 or 3 a week).
Zophobas can be gutloaded with cereal, oats, bread, carrots, apple, sweet potato and collard greens. They will get their moisture from apple etc. so do not mist or offer water.
-Brad