This box should be half-filled with fine meal or flour to which some middlings or bran is added. A few scraps of cloth or wrinkled paper will assist in preventing the meal from packing too solidly. Proper ventilation and a fairly even temperature are essential to prevent mold growth. Cheese cloth tied over the tray will provide ventilation while preventing the escape of the adult beetles. A two inch strip of sheet metal should be securely nailed to the inside walls of the tray above the food mixture to prevent the insects from crawling over the side.
Some moisture is necessary.
This may be best provided by the addition of some moist foods such as pieces of raw potatoes, carrots, ripe apples or banana peels. These should be placed on the surface of the mixture and slightly dampened every few days. After the tray has been prepared and mealworms added, the tray should remain undisturbed for several weeks to allow the worms to develop. The larger worms will then have changed into the pale, quiet stage which later changes into the adult. The colony should then be prepared for expansion.