Mealworms Life Cycle

Mealworms are the larvae of the beetleTenebrio molitor. During their life cycle these beetles undergo complete metamorphosis: egg, pupa, and adult. Times required for each stage under average conditions are listed below.

Egg.......4 weeks
Larva....10 weeks
Pupa......3 weeks
Adult.....4 weeks

Culturing Mealworms

Mealworms are handy for feeding to a variety of animals, such as birds, bats, amphibians, and reptiles. To culture mealworms, use a plastic, metal, or glass container with smooth sides to prevent escape. Cover the colony with a screen; secure the screen with an elastic band. The size of the container will be determined by the number of larvae to be cultured:

wide-mouth gallon jar....1,000 mealworms
15 x 12 x 6 inches........5,000 mealworms
36 x 24 x 12 inches.....50,000 mealworms

NOTE: To discourage mites from invading the mealworm colony, place the container in a bowl of water.

Feeding Mealworm Colonies

Use any of the following mixtures:

1. Wheat bran
2. One part pulverized dry cat or dog chow + 3 parts wheat bran
3. Quaker oats + 1/2 cup bone meal powder + 1/4 cup multivitamin powder

Cover food and mealworms with 2-3 layers of moistened burlap. Sprinkle with water once weekly to maintain moisture level in colony. Burlap also simplifies collecting mealworms. The larvae gather between the burlap layers and can easily be scooped by hand or picked out with forceps.

NOTE: Mixtures of foods, such as oats, intended for human consumption are less likely to contain contaminates, such as mites, that can destroy a mealworm colony.

Moisture

Lay slices of apple, potato, carrot, or over-ripe banana over the surface of the colony to provide fluids for the mealworms. In addition to obtaining moisture from these vegetables and fruits, mealworms lay their eggs on them. Collect these and save them when starting a new colony.

Temperature

Mealworms thrive in a warm (80-90 degrees F) environment. To maintain the larvae in a state of dormancy, cover the container with cloth to prevent condensation, and set in the refrigerator (40-50 degrees F). Mealworms will die at lower temperatures.

Cleaning the Colony and Starting New Colonies

Over time, a build-up of powdery residue will appear in the container. This residue, called frass, consists of mealworm wastes and eggs. Sift this out once a month using a colander, window screen, or tea strainer. Keep frass in a separate container and add bran and potato slices. The eggs will hatch in about one month. Two weeks after hatching, sift out the tiny larvae and put them in a container with fresh food, burlap, and vegatable slices as described above.

Quick definition ...

bur·lap (n.)

"A strong, coarsely woven cloth made of fibers of jute, flax, or hemp and used to make bags, to reinforce linoleum, and in interior decoration."

R. Bessin, Univ. of Kentucky

Mealworms are the larval stages of a common darkling beetle and are pests of flour, meal, grain and related products. They vary in size from the very small, newly hatched worms to full grown larvae that are approximately an inch long.

These worms may be easily raised at home by following a few suggestions.

An initial supply may be obtained from dealers or found in feed, grain, or meal in a barn or feed room. A wooden box or box eight to ten inches deep, twenty four inches long and eighteen inches wide makes a satisfactory rearing container. 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. A little bran may be sprinkled on the surface of the mixture and a few pieces of apple and carrot added followed by a second sprinkling of bran. A close watch should be kept for several weeks until a number of adult beetles appear.

Another tray should then be provided, prepared with the same food mixture as in the first. The adults should be placed in this tray to lay eggs for more young worms. As soon as these young worms have grown sufficiently to be handled they should be put in the first tray and allowed to grow as large as desired. By using a two tray system, one should be able to provide a continuous supply of worms.

The food mixtures must be discarded, the trays cleaned and scoured, and a freshly prepared food mixture put in occasionally for the successful rearing of the worms. Old food mixtures will become foul unless occasionally changed.