How to Raise Mealworms

By Stephany Elsworth
Lizards, turtles, birds, fish and other animals eat mealworms.

Mealworms (Tenibrio molitor) are the larvae of a type of darkling beetle. Mature mealworms are around an inch long, with legless, segmented golden-brown bodies. You can purchase them in pet stores as animal food or fish bait, but they can be expensive in large quantities. Some pet owners choose to grow their own mealworms at home.

Prepare your mealworm habitat by cutting a hole out of the middle of the lid. Cut out a section of fine-mesh window screening material that is approximately 1/2 inch larger than the size of the hole. Glue the window screen to the inside of the lid.

Fill the bottom of the container with several inches of a grain-based substrate such as uncooked whole-grain oatmeal, wheat bran, cornmeal, whole wheat flour or oat bran. Sprinkle some dry brewer's yeast, skim milk or bone meal in the substrate to encourage insect growth. Cover about two-thirds of the food surface with two or three layers of cloth or newspaper, leaving space between the cover and the edges of the box. Place an aluminum pie pan in the uncovered portion of the meal.

Purchase live mealworms online or in a pet store and allow them to develop for several weeks. Add moisture to their diet by placing slices of apple, potato or cabbage in the pie pan. It will mold, so remove and replace it every two to three days. You can also sprinkle their food with calcium or vitamins.

Mealworms remain in the larval stage for around 10 weeks and molt approximately 15 times before pupating. Mature larvae curl up in a ball and turn into large whitish pupa, and remain in the pupal stage for several weeks before morphing into adult beetles. The adult beetles begin laying eggs between one and three weeks after they emerge. The larvae usually pupate between the layers of newspaper or cloth, and adult beetles lay their eggs on the cloth or in the food.

Collect the mealworms that you need by withholding moist food for a day or two, then add a wet paper towel or a moist lettuce leaf to the substrate. The worms will gather on the moist material. Shake them off into a separate container. You can also use a sifter or strainer to separate the worms from the substrate.

Tip

Some mealworm growers separate the adult beetles from the larvae and eggs and house them in their own container, because they tend to lessen production by feeding on the eggs.

Mealworms thrive in room temperature and require approximately 70 percent humidity. You can add a moist sponge in a shallow container or baggie to generate additional moisture.

Avoid cultivating mealworms in small containers. Overcrowded containers tend to overheat, which kills the larvae.

Warning

People who have asthma may want to wear a mask and gloves when working with mealworms. A 1994 study by A. Siracusa et al. from the Institute of Occupational Medicine at the University of Perugia, Italy noted that the larvae of insects commonly used as fish bait might exacerbate asthma or other respiratory issues.