Mealworms are the brown worm-like larvae of darkling beetles. They are the second of four stages of life and exist to eat and grow until they have enough energy stored to begin transformation into pupae and then beetles.
Mealworms can be found throughout most of the world where they prefer warm, dark, and damp places like under decaying logs and leaves. They are designed for burrowing and eating and will feast upon grains, vegetation, spoiled food, and many other types of fresh or decaying organic matter.
These insects are an important part of the ecosystem. Their voracious eating habits aid in the decomposition and cleanup of unwanted organic matter. They are also an important food source for many animals. In the wild, birds, spiders, rodents, reptiles, and other insects prey upon them.
Unfortunately, their eating habits and affinity for grains also make them pests in the modern world. Mealworms can get into and ruin stored flour, pet food, mill feed, cereal and other dry goods.
Mealworms are a popular feeder insect for bearded dragons, bluebirds, chickens, fish, and many other animals. They are high in protein and fat and are easy to maintain. They are available live or pre-killed and dried.
Live mealworms can be stored in a refrigerator for months. All you have to do is take them out of the refrigerator about once a week and give them some food for a few hours. They are also easy to raise and reproduce in large numbers. A female darkling beetle can lay hundreds of eggs.
Dried mealworms are worms that have been freeze dried or slowly oven dried. Dried worms usually float which can make them a great treat for ducks and fish. They retain much of their nutrients, last longer than live worms, and are easily stored until needed.
Raising & Breeding
Raising mealworms is fairly easy since they are prolific breeders and are hardy insects. It is also fairly inexpensive and can save you quite a bit of money if you use a lot of worms every month. They rarely smell, are easy to care for, and don’t take much work.
Breeding will take a while to get started, but once there are plenty of beetles laying eggs you will have worms for as long as you need. You should start with at least one hundred mealworms, but can begin with many more. Then, all you need is a container, substrate, and a source of food and water.
The container should have a large surface area and smooth sides. The sides of the container only need to be a couple inches higher the substrate in order to prevent the worms from escaping. An aquarium, terrarium, plastic box, or Sterilite container will make an excellent home.
The container will also need a screened lid to prevent other insects and creatures from getting in and to allow airflow. Good ventilation is needed to prevent the container from getting to warm and to prevent the buildup of humidity and mold growth. If you are using an aquarium, there are screened lids available. For a plastic box you can cut away most of the lid and attach some window screen.
The substrate of the container will be the food. You can use wheat bran, oatmeal, cornmeal, wheat flour, Wheaties, Cheerios, ground up dry dog food, or a mixture of these dry foods. Fill the bottom of the container two or three inches deep with the food substrate. You will have to add more food regularly since mealworms are big eaters.
Slices of potatoes, apples, carrots, lettuce, cabbage, or other fruits and vegetables can supply water to your worms. Potatoes are often preferred since they last a while and do not mold quickly. Do not use a bowl of water since mealworms will crawl in and drown.
Temperature, Lighting & Humidity
The ideal temperature for growing your colony is around 75 degrees F. A heat emitter may be necessary if you are in a cold climate. You will want to keep the container away from windows and direct sunlight to prevent it from becoming too warm.
Light is not necessary. A normal day and night cycle of light will be fine.
You colony of mealworms will reproduce more quickly with a higher humidity, but for most areas the natural humidity in the air will be sufficient. If you live in a dry climate, you can place a smooth glass or bowl of water into the container to raise the humidity. Make sure the water container is tall enough to prevent the worms from crawling in.
Any dead worms, pupae, or beetles should be removed from the container regularly. If the container begins to smell like ammonia or becomes moldy, it is time to clean the container. You will need to remove all of the mealworms, beetles, and pupae, discard the food and waste, and clean the container. Once clean, replace the food substrate and return the insects to the container.
It is helpful to have a second container to aid in raising mealworms and keeping them odor free. After your colony is going strong, you can move any beetles to the second container where they will begin a new colony.
By the time the second colony is established, the original container should have very few mealworms. You can move any remaining worms to the second container and the original container can then be cleaned and prepared to repeat the cycle.
Mealworms that birds, reptiles, and other animals love aren’t really worms. They are the larvae of darkling beetles. There are over 20,000 different types of darkling beetles and mealworms come from the species Tenebrio molitor.
A darkling beetle experiences complete metamorphosis which means that it has four distinct stages of life. The four stages are egg, larva, pupa, and adult. The amount of time a darkling beetle spends in each stage can vary greatly due to environmental factors like temperature, humidity, food, and water.
The first stage of life is spent as an egg. The white bean-shaped egg is tiny and about the size of a speck of dust. The egg is sticky and is quickly concealed by dirt, dust, and substrate. It will take around one to four weeks for an egg to hatch and the larva to emerge.
The second stage of life lasts about eight to ten weeks and is spent as a brown larva. This is the stage where the insect is a mealworm. When first hatched, it is quite small but will grow to one to one and a half inches long.
Since it has a hard exoskeleton, the worm will need to molt and shed its hard outer shell in order to grow. Molts will occur ten to twenty times during this stage of life. A recently molted worm will be soft and white, but the exoskeleton will quickly harden.
A mealworm spends its time eating and growing in order to save up energy for the next transformation.
During a mealworm’s last molt it will turn into a white alien-like pupa. It has no mouth or anus so does not eat. It does have leg and wing buds, but they do not function. The pupa is quite helpless and the only movement it can do is wiggle. This stage of life will last one to three weeks as the pupa transforms its organs and body into an adult.
The final stage of the insect’s life is as the darkling beetle and lasts one to three months. The beetle will be white with a soft exoskeleton. As the outer shell hardens, it will turn brown and then black. The beetle does have hard wings, but it is unable to fly.
After about one to two weeks of adult life, beetles will begin to mate and reproduce. A few days after mating, female beetles will burrow into soil or substrate and lay eggs. Darkling beetles are prolific breeders and females can lay hundreds of eggs during their adult lives.
The mealworm is a worm-like larva with a hard exoskeleton. Its body is designed to burrow, eat, and store fat. There are three distinct sections which are the head, thorax, and abdomen.
The head of the mealworm has the mouth and labrum, a lip-like mouth part, to aid in its voracious eating habits. The mouth and its parts are quite small and designed to eat small pieces of food.
There is also a pair of antennae and larval eyes. The antennae act as feelers for the worm as it digs in search of food. The eyes are small and poorly developed due to the insect’s burrowing nature.
The thorax consists of three segments called the prothorax, mesothorax, and metathorax. Each segment has a pair of short legs. A mealworm doesn’t walk very well, but its legs and claws are perfectly suited for burrowing.
The abdomen has nine segments with the last segment containing the anus and a spine. The abdomen contains the digestive tract and stores lots of fat from all the food the mealworm eats. This fat will eventually be used for the worm’s transformation into a pupa and then a beetle.
Recipes & Nutrition
Mealworms are nutritious insects that are high in protein and fat. They are a good food for birds, reptiles, small animals, and even people.
Although eating insects may sound strange, for most of the world eating insects is quite common. Some are even considered a delicacy. Mealworms can be eaten raw and alive, they can also be pan-fried, but dry-roasting is often the tastiest and least recognizable way to eat them.
Dry Roasted Mealworms
Dry roasting is a good way to store excess mealworms. Dried worms don’t take up much space and can last up to a year without being refrigerated. Roasting removes the moisture from the insects while retaining much of their protein and nutritional value.
Eating Dry Roasted Mealworms
Dry roasted mealworms can be salted or dipped in chocolate and eaten as a snack, sprinkled on salads, and added to soup. They taste a lot like peanuts and can replace nuts in cookies, cakes, and other desserts.
Since roasted worms are brittle, they can be ground and mixed with flour when you bake muffins, pancakes, or bread. The different ways these insects can be added to recipes is almost limitless.
How to Dry Roast mealworms
Place your live mealworms in a colander and toss and rinse them under cool water. This is to remove any food and substrate from the worms. Be sure to pick out any dead worms or pupae.
Pat the worms dry with paper towels, place them in a container or plastic bag, and put them in the freezer for about fifteen minutes. This will quickly kill the worms.
Spread the mealworms out evenly on a non stick cookie sheet. If you are worried that the worms may stick, you can lightly grease the sheet.
Place the worms in an oven at 200 degrees and bake them for one to two hours until they are dry and crispy. Some people do not like the smell of baking worms and prefer to cook them outside on a gas grill set to a low temperature.
NOTE: If you are roasting a large quantity of mealworms, you can use a roasting pan instead of a cookie sheet. They may also need to be baked for a couple more hours.
Live Mealworm Nutritional Values*
Dried Mealworm Nutritional Values*