A crawling collection of mealworms.
Mealworms to Feed Your Pets

Feeder Animals Information Sheet: Mealworms

Mealworms are the larval stage of mealworm beetles. Their scientific name is Tenebrio Molitor, and they are a species of darkling beetle. They are found almost worldwide in dark, warm, damp places, such as beneath decaying vegetation. They are composters of organic material and are an important part of the Earth’s ecosystem. In nature, mealworms are prey for rodents, reptiles, spiders, birds, and larger insects.

A crawling collection of mealworms.
For most reptiles, this is a buffet. Photo by Robert Gunnarsson on Unsplash.

Size and Lifecycle of Mealworm Beetles

The first stage in the mealworm lifecycle is spent in the egg. The white eggs are tiny, about the size of a speck of dust, and bean-shaped. The eggs are sticky and easily cling to dirt and substrate. They take 1 to 4 weeks to develop before the mealworms hatch. The newborn larva will remain in the stage of brown worms for 8 to 10 weeks. Mealworms eat until they have grown enough to mature into pupae, and then into adult beetles. They have hard exoskeletons that they need to molt as they grow. Molts occur between 10 and 20 times during the larval stage. Freshly molted mealworms are soft and white, but quickly darken and harden. Mealworms grow up to 1.5 inches in length before transitioning to the pupae stage.

Mealworms molt one last time before becoming pupae. You should prepare a secondary container for the pupae, as both mealworms and adult beetles will feed on them. You can place the pupae in a container lined with paper towels, which they will stick to as they transform. Pupae have wing buds and legs but do not use them and have no mouth or anus. Pupae do not eat; they spend all their stored energy in the transition. The pupae stage lasts 1 to 3 weeks as the pupae transitions into the adult body.

The final adult stage of the darkling beetle lasts 1 to 3 months. Adult beetles are initially white and soft, but they shortly darken to black and become hard. The adult beetles have wings but are unable to fly. After 1 to 2 weeks of adulthood, beetles begin to reproduce. A few days after mating, the females begin to burrow into the dirt and lay the eggs. Females can lay hundreds of eggs during their adult stage. Overall, the amount of time the mealworms spend in the various stages depends on environmental factors, such as humidity, water, food, and temperature.

Pros and Cons of Using Mealworms as Food

It is important to weigh your options when you pick mealworms as a food source for your pet. You may want to keep the mealworms for a while, or you may want to use them immediately. You could already have a food source for your pets that achieves the same nutritional output of mealworms. Let’s examine the benefits and drawbacks of mealworms.


  • Mealworms are high in fat and protein.
  • A broad range of reptiles, birds, and amphibians will eagerly feed on mealworms.
  • Both the larva and the adult beetles are edible.
  • They are cheap and easy to care for, swift to breed, and odorless.
  • The beetles and worms eat the same food and can be kept in the same container.
  • They are commercially available as live insects or pre-killed and dried.
  • Dried mealworms float, which makes them a convenient treat for fish and ducks.
  • They retain nutrients when dried and are easily stored.
  • Dried mealworms also have a shelf life of up to 1 year.
  • Live mealworms can have an extended shelf life by being stored in the refrigerator for several months, but must be fed once a week


  • Live mealworms are voracious eaters, and if they escape, they can get into and ruin dried foods for humans and other pets.
  • Mites or parasites can quickly infest mealworm colonies. However, these infestations can be avoided by keeping the contents of the container dry. If the colony does get infested, throw the colony away and thoroughly sterilize the container before beginning a new colony.
  • Mealworms must not be a constant food source; instead, they must be a part of a varied diet.
  • Due to their high fat and protein content, mealworms will be more popular as a food source than any other feeder insects.
  • Any pet that eats only mealworms will grow overweight.
  • Certain reptiles and amphibians are too delicate to digest the hard exoskeletons of mealworms.

Ultimately, you should consider the diet of your pet, your storage capabilities, the cost of mealworms, and the effect the mealworms have on your animal. Although mealworms are a common food source, they may not be suitable for every pet.

Nutritional Content of Mealworms

Every 100 grams of mealworm larvae contain 206 calories and a range of 14 to 25 grams of protein. The larvae contain levels of minerals such as iron, zinc, copper, sodium, and potassium that are akin to the levels found in beef. They also contain linoleic acid, an essential nutrient. By weight, they also contain high levels of most vitamins. Dried mealworms have a higher protein and vitamin content by weight than live mealworms, simply because the desiccation removes the water weight.

Caring for Mealworms

Mealworms ready to be used as a meal.
Mealworms prepped in substrate, ready for feeding.

Live mealworms should be kept in a tub with good ventilation and a large relative surface area. If you see condensation below the lid of the container, ventilation must be increased. The floor space is more important than the height of the walls of the container. Use a metal, plastic, glass, or wax-coated container with smooth sides so the mealworms cannot crawl out and infest your home. For air, punch out small air holes across the lid or remove larger sections of the lid and cover the hole with a fine mesh or a pair of old pantyhose. However, if the container is deep enough, a lid is not needed. A screen or lid will help keep other insects out of the container.

Mealworms are nocturnal, so house them in a dark area. Mealworms can be kept at room temperature, but they can breed more quickly at higher temperatures and in higher levels of humidity. However, it would be best if you did not subject them to temperatures above 80° Fahrenheit. If you live in a colder climate, use a small heater to keep the container around 75° Fahrenheit. Keep the mealworms out of direct sunlight, as the high temperature can overheat the mealworms. If you live in an arid climate, place a smooth-sided bowl of water in the enclosure that the mealworms will not be able to crawl into.

Cover the bottom of the container with an edible substrate, 2 to 3 inches deep. This acts as both bedding and food. The substrate can be a combination of ground cereal grains, such as corn, oats, wheat, and bran. You may also include ground dry dog food. Replace the substrate as it gets eaten. Fully replace the bedding every few weeks, or sooner if you observe a stench or mold. Use a sifter to separate the worms from the bedding when you replace the substrate.

To provide hydration, give the mealworms slices of carrots, apples, or potatoes. There is no need to provide a bowl of water; the food will provide a well-rounded diet and plenty of moisture. You can also feed the mealworms lettuce or cabbage leaves, as well as most other fruits and vegetables. Potatoes are most efficient since they take longer to spoil than most other produce.

If the mealworms are dying faster than you can feed them to your pet, store the excess mealworms in the refrigerator. Keep the fridge temperature above 40° Fahrenheit so they do not die from the cold. Regularly remove all dead beetles, pupae, and worms from the container. A second container will help with storage while you clean the main container.

Gut Loading Mealworms

Between 12 and 24 hours before you plan on feeding the mealworms to your reptile, allow the worms to gorge on various foods for at least 12 hours. Most of the larvae will relieve themselves within 24 hours of eating, so use the gorged worms as prey within this period so that the worms still carry the nutrients. It’s best to feed the larvae to the reptiles as soon as they finish gorging. This process is known as gut loading [LINK]. For reference, a handful of baby carrots can be enough for about 500 mealworms. The foods should be high in calcium and low in sugar. Avoid foods that are high in phosphorus, as it can inhibit calcium absorption. Without sufficient calcium, your reptiles will become subject to metabolic bone disease. The mealworms will carry the nutrients of the food in their digestive tract and provide nutrients beyond the fat and protein they naturally possess. Collard greens, squashes, and carrots are all high in the necessary nutrients that your reptile needs. Although mealworms are only a small portion of your reptile’s diet, they should still be allowed to gut load to carry the vitamins and minerals that your reptile needs.

The final way to ensure a fully balanced mealworm is to dust it with a calcium or multivitamin powder. Place the gut loaded mealworms in either a plastic container with a lid or a sandwich bag, and sprinkle in about a quarter of a teaspoon of the substance. Seal the container and shake it gently to coat the larvae.

It is recommended to have a separate container reserved for gut loading. This ensures that only the mealworms you intend to use are allowed to gut load, and the food is not parceled out among the whole colony. Simply move the desired amount of mealworms into the container with the gut loading supplies. A six-quart tub should easily suffice for the gut loading. Keep the gut loading container in dim light, as this mimics the natural environment that mealworms will eat in. In many cases, mealworms may not gut load in bright environments.

Keep the temperature of the gut loading container around 78° Fahrenheit.  If you have removed the mealworms from the refrigerator, allow them to come up to temperature before making the food available for gut loading. Avoid the cereal grains that are a part of the regular diet when gut loading. You should also avoid broccoli, soybeans, nuts, spinach, and seeds. These foods all interfere with calcium absorption in your reptile.

Need Mealworms for Your Pet?

If you want to learn more about mealworms, how to feed them to your pets, or where to purchase them, get in touch with Allan’s Pet Center. We have a supply of mealworms, both live and dried, available for purchase. We can answer all your questions about storage, feeding, and nutrition.

Allan's Pet Center

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