Mealworms are darkling beetles (Temebrio molitor) in their larval stage, the second of four life stages for these insects. You may find mealworms living in dried grain products in your cupboards.
Mealworm Life Cycle
Mealworms hatch from white eggs about 14 days after laying. They molt between nine and 20 times in the larval stage. Mealworms then enter the pupa stage. The pupa is a white sac that's a half-inch to three quarters of an inch long. The pupa stage lasts for two to three weeks. Within the pupa, the mealworm is completing transformation into a beetle. During the pupal stage, the mealworm does not move or eat. The pupa's color darkens before the mealworm hatches as an adult beetle. As soon as two to three weeks after emerging from the pupal stage, adult females begin to lay eggs.
These insects have yellow or brown wormlike bodies. Their bodies are hard, to allow the mealworms to easily burrow. Adult mealworms are approximately 1 inch long.
Adult darkling beetles are black with hard wings and segmented antennae near the eyes. Some beetle species have scent glands in the rear of the body. When threatened, adults will lift their bodies and spray a potential predator. The chemicals released turn the skin brown and have a bad odor.
Mealworm Habitat and Diet
Mealworms' ideal habitat is a dark, moist location where they have access to food and won't be disturbed. They are often found in stored grain containers, in garden and bird seed, and under accumulations of organic matter such as leaves. In addition to eating grains, mealworms feast on dying leaves and grasses, feces and dead insects.
Place mealworms in a plastic container such as a cup or margarine container. Use a clear one if you want to allow easy observation. Make sure the container has a lid with air holes. Place a thin layer of bran or crushed wheat flakes on the bottom of the container. Feed the mealworms a slice of apple or potato. Provide fresh food regularly and don't allow food to mold in the container. Mealworms get their hydration from their food, so don't supply a water source.