Keeping and Breeding Mealworms (Tenebrio molitor)

Mealworms are the larvae of the darkling beetle, and they eat a variety of grains. They were often found in flour, hence the name. "Millworm" may be a regional variation on the common name. This care sheet may also be used for the smaller "mini-mealworms"--they can be kept in a smaller container.

To set up a mealworm colony, you'll need a plastic shoebox style container--16 qt minimum. Some people prefer to use several shoeboxes. Put a couple inches of a cereal product in the box--bran, baby cereal, an unsweatened cereal such as Wheaties (crushed), etc. Add at least 50 mealworms, and a piece of carrot, apple, or wrung-out paper towel or tissue for moisture. Don't overdo the moisture, as this can lead to mold which will kill the worms. Replace it after it's completely dried out. They need less moisture than you might think. I've been extremely pleased with the results of using soaked tissue or paper towel for mealworms--they will chew the tissue into a froth that will wind up covering the surface of the substrate. It holds in just the right amount of humidity to keep the worms in excellent health, but does not cause mold to grow. You may want to use non-bleached paper towel if you're concerned about chemicals.

Depending on their size, in a few weeks the worms will metamorphose into pupae, and then emerge later as darkling beetles. Some people move the pupae into a new container, stating that the mealworms will sometimes eat them, but I have not personally had this problem in my colony. The beetles will mate and lay eggs in the substrate. Some people will wait several days, then move the beetles to another container, so that there will be eggs in each container. After what will seem like a very long wait, minute mealworm larvae will hatch. Care for them the same way you did the original larvae, until they are big enough to use as feeders. Save a good number of them to metamorphose into darkling beetles and keep the colony going.

Before feeding mealworms to your reptiles, you may wish to gut load them with additional foods--move a number of the worms to another container, and provide them with the foods you want to put into your herps, such as fresh dark green leafy vegetables, carrots, oranges, etc. Do this for about 24 hours before feeding them off. Do not give them calcium powder, however. If you do this, the worms will most likely die, usually within a day or two. Some commercial gutloading products contain a lot of calcium--do not leave the worms with this for longer than 12 hours before feeding them off, and do not put them back in your colony after they have been eating it.

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