Mealworms are some of the most popular feeder insects for reptiles and amphibians, and among the easiest to raise and care for. These little critters are highly nutritious for pets such as lizards and frogs – and if you so desire, you can munch on a few as well! If you’re searching for the great feeder insect read on to learn all about the delectable mealworm.

What is a Mealworm?

A mealworm is not actually a worm at all! In fact, it is just one of the four life stages of the darkling beetle, otherwise known by its scientific name, Tenebrio molitor. There are over 20,000 different types of darkling beetles currently known, so you may have run into a few variations in your search for the best food for your reptile.

Many of the larvae tend to look quite similar in appearance, but there are many aspects of their life cycles and behavior that can help you distinguish between the common feeder species. For instance, the T. molitor mealworm is a cream to light brown color in its early days as a larva, with a segmented body – each portion distinguished by a dark brown line. As it ages and approaches adulthood, its body darkens.

Mealworm Life Cycle

The mealworm has four total life stages:

  • Egg: You can recognize mealworm eggs, or darkling beetle eggs, to be more exact, by their shape, appearing as a small, white, bean-shaped bit of dust. It will be difficult to spot if found in the mealworm's natural habitat, as it is normally concealed by wheat bran and other substrates. The mealworm will remain in this substrate between 1-4 weeks.

  • Larva: This stage, known to many as the “mealworm,” of the beetle’s life cycle lasts for an average of 8-10 weeks. It starts relatively small but quickly grows to its maximum size of 1" in length. As it grows, the mealworm needs to molt, or shed its exoskeleton. Molting can occur up to twenty times during the larval stage. During this time, the larva eats and saves energy for growth into adulthood. This is why it is so nutritious!

  • Pupa: This is perhaps the strangest-looking life stage of the life cycle. During the final molt of the larval stage, the mealworm metamorphosizes into a curled-up pupa. At this time, it no longer has a mouth or anus, and therefore cannot eat. Although it does have legs and little buds as the beginnings of wings, it cannot move these body parts, and is instead, completely still. This lasts for about 3 weeks as the organs develop for adulthood.

  • Adult: Lasting for about 1-3 months, the darkling beetle adult is initially white with a soft exoskeleton that hardens over time. While the shell hardens, it becomes darker in color, first turning brown, and then black. Despite having wings, the beetle cannot fly. It begins to reproduce only days into adulthood, giving you plenty of time to raise a new generation of mealworms.

Where Are Mealworms Found?

Mealworms are native to several countries of Africa, however, humans have distributed them throughout the world, and they have become a naturalized species of North America. They can be found happily burrowing in dark, moist soil, where they feed on decaying organic matter such as rotting wood and leaves. They can be found sneaking a bit of space in animal dens as well.

In captivity – or in cities and human-centered landscapes – mealworms will take refuge in similar habitats but will feed on grains, spoiled and rotting food, and natural vegetation instead. Anywhere they live, they are an incredibly important part of their ecosystem, as they clean up organic matter that may otherwise be left out and become unsightly or give off foul odors.

You are most likely to find mealworms in human environments than in the wild, though. Because food waste is so abundant, it’s easier for them to find nutrition in such landscapes, especially in home kitchens, grocery stores, warehouses, and farms.

What Pets Eat Them

Mealworms are packed full of nutrients for your pet.

Compared to other species of darkling beetle larvae, the mealworm has more “meat” on its body and therefore offers more protein than others. The most common animals that eat mealworms include:

  • Birds

  • Geckos

  • Turtles

How to Raise Mealworms

Raising mealworms is surprisingly easy and one of the best ways to save money when caring for a reptile. If money is not your concern, keeping mealworms is also just a fun hobby that many people share, since they make simple pets that demand very little from their keeper. They are extremely prolific breeders and resistant to harsh environmental conditions, so you can grow a lifetime supply of this nutritious snack for your reptile (and yourself!) with little effort.

To get your mealworm colony started, follow the instructions below:

1. Set Up the Container

Mealworms are not too picky in the material or size of their container. Although they will need a container about 5” deep minimum, they can be packed in there with over 100 individuals. The ideal mealworm container will have a large surface area – the best containers being aquariums, terrariums, or large Tupperware.

To prevent the mealworms from escaping while still providing airflow, you’ll need a screened lid – poking holes in a plastic lid may not be the best option, as you need to make sure that other creatures do not get into the container and wreak havoc in the colony. Ventilation is also essential to preventing mold and harmful bacterial growth.

(If you only have a plastic lid available, you can cut away the center of the lid and attach a cut section of window screen or similar material to it.)

2. Add Food as Substrate

The substrate will serve a dual purpose: functioning as a “soil” that the worms can burrow into and take refuge in the darkness that they naturally prefer while simultaneously providing them the necessary nutrition they need to grow. The perfect foods to provide include:

  • Wheat bran

  • Oatmeal

  • Cornmeal

  • Wheat flour

Layer your substrate until it is about two inches deep. You can choose to mix the food with commercial mealworm substrate, although it is not required and will not make a significant difference to the health of your colony. No matter how you prefer to set it up, you will have to regularly check the container to replenish it as the mealworms chip away at their snacks.

For hydration, you’ll want to avoid adding a bowl of water since mealworms will simply crawl in and drown. Instead, give them foods such as apples, potatoes, and carrots to quench their thirst. (Potatoes are the best since they can last long in the container without molding.)

3. Maintenance of the Container

Keep your container at a temperature of 77 F – this is the best temperature for the worms and most accurately replicates their natural habitat. To do so, you may need to provide a heat lamp or other constant source of heat, while ensuring that there are not placed next to a window or other area where too much sunlight may come through.

It is not necessary to give the colony light, however, if you do, do your best to keep them on a regular day/night schedule. Your colony will reproduce at higher rates if their container is humid, but this needs to be monitored closely to avoid the growth of mold or fungus.

Lastly, remove any dead larvae, pupae, or adults or the worms will become cannibalistic and no longer feed on the substrate you’ve provided. Females can lay hundreds of eggs at a time, so you’ll need to pay regular attention to both death and birth rates in your colony!

Mealworms are some of the most nutritional insects you can feed your insect. They are rich in protein, and depending on how you choose to feed, can provide your pet with lots of water as well. The species can survive for quite a while in this larval stage, so if you prefer, you can simply store them in the fridge with intermittent feedings after purchase (if live) or raise your own colony instead. Either way, they will provide your reptile with a great addition to a rich, well-balanced diet.