Mealworms are a larval stage of the Tenebrio molitor or mealworm beetle. This beetle is one of the darkling beetle species. An adult mealworm beetle’s size ranges from 1.25 to 1.8cm, and it is often black or dark brown. Do not confuse them with the lesser mealworm or litter beetle Alphitobius diaperinus.
On the other hand, mealworms, which are not worms but grub or larval stage of the Tenebrio molitor, are about ½” – 1″ (1.2-2.5 cm) or much bigger with 200 of them will weigh about an ounce. It is common to get a full-grown mealworm longer than 1 inch and are either golden or yellowish.
Although they are edible as human foods, especially in Southeast Asia, their most common uses are for feeding pets and other animals like:
- Reptiles including turtle and tortoise, basilisks, bearded dragons, sailfin lizards, fringed-toe lizards, water dragons, chameleons, small snakes, among others
- Amphibians including frogs such as dart, salamanders, newts, toads,
- Invertebrates such as scorpions, praying mantis, giant insectivorous spiders, centipedes
- Small mammals such as sugar gliders, moles, mice, voles, shrews, hedgehogs,
- Birds including chicken, turkey, peafowl, chukars, ducks, quails, peafowl, and other smaller birds, once they are at least 4-6 weeks of age.
- As fishing baits
- For compositing
Also, they may help in the degradation of polystyrene without been affected in any way when compared to those that eat healthy foods.
Fried or Edible or mealworms for human consumption
We will not be focusing on safe mealies for eating by humans, including ground ones that may make burgers or tequila candies. If you need them, many vendors sell spicy, flavored, unflavored, roasted, or fried mealworms.
Life in the wild mealworms
In the wild, they feed on fresh decomposing vegetation, feces, dead insects, dead and dry small rodents, and other organic matter. They aid in the decomposition of organic matter in the soil.
Lifecycle and reproduction
They undergo complete metamorphosis, i.e., egg, larva, pupa, and adult stages. How long each of these stages takes will depend on temperature, food availability, humidity, and water. Therefore, their lifespan can be from 4 months to about a year.
Once they turn into adults, they will take a week or two to begin reproducing. The male mealworms will release a sex pheromone to attract a female. Inbreeding reduces how effective this pheromone is, and most females are attracted to the odors of outbred males than inbred males.
What follows is mating where the male will chase the female, mount it, and inject a packet of sperm via its aedeagus.
A few days later, the female will look for a dark place with soft soil or substrate and lay white, bean-shaped small eggs. The eggs will take 4-19 days before hatching. A warm and humid environment will favor faster hatching.
After a week to a few weeks after the female laying eggs, you will see mealworm baby larvae, which will be about 3 mm in size.
Larvae and refrigeration effect
At the larval stage, mealworms have a hard exoskeleton, and leading activities are to burrow, eat, and stores a lot of fat for transformation to pupa. Molting occurs in between each of its larval stages to allow them to grow, and they molt 10-20 times.
During molting, they shed their hard cornflake-like exoskeleton, and immediately after molting, they white, and their exoskeleton is not as hard.
However, if kept in a fridge at about 40-50 degrees Fahrenheit, they will stop growing until they are brought to warmth again.
They stay in the larval form for 4-10 weeks before they transform into pupae or even up to several months, especially during winter.
Immediately after transforming into the pupal stage, they will appear white but later turn yellowish-brown or brown. During this stage, they do not eat and take 3-30 days before they metamorphose into beetles. How soon it occurs will be influenced by temperature and other environmental factors.
Once they have turned to adults, they will live for 1-3 months, but breeding begins after one to two weeks.
Nutritional composition of fresh live mealworms 
- Moisture 44%
- Fat 72%
- Protein 27%
- Fiber 73%
- Ash 57%
- Ca, ppm 133
- P, ppm 3345
- Ca:P ratio 1:2.5
Nutritional composition of fresh live mealworms
- Proteins 24%
- Fats 87%
- Fiber 61%
- Ash 18%
- Ca, ppm 133
- P, ppm 3345
- Ca:P ratio 1:2.5
Raising Mealworms for Sale or Use
Raising healthy mealworms with stamina is not so difficult. You need a few things and have a good care and maintenance schedule. Let us look at what it takes.
Why keep mealworms?
If you have birds, reptiles, fish, amphibians, or small mammals, you should consider rearing your mealworms at home. Why? It is simple. Raising them will go a long way in saving the cost of having to buy live or freeze-dried mealworms, including the shipping and logistic costs.
Furthermore, they have a high efficiency of converting food to bugs, are easy to keep with minimal requirements, and require a small raising space.
Thirdly, they are prolific breeders with a single female mealworm beetle able to lay as many as 500 eggs (typically, 200-300 eggs).
Unlike crickets, which can be noisy and smelly, meals are much quieter and with good hygiene, and they will be odorless. Nevertheless, since they can move but not so much, they are easier to feed to these pets.
Besides keeping them for personal use, you can raise and breed them for sale to people who want to eat or give them to their pets. It is an inexpensive, easy to start, profitable venture, that is space economical and requires a very little initial capital investment. Why not try breeding mealworms for profit?
Finally, to have them, you need to get live mealworms or beetles (both male and female), one or more containers, food, and a few other things. Here are the details:
House or keeper
Choose a keeper with a large surface area to allow you to keep so many. Plastic containers such as Rubbermaid, glass containers, terrariums, aquariums, or any other sterile container that has a smooth edge is ok.
For instance, 50,000 to 100,000 larvae can grow in a Sterlite 64 Quarts container. The surface area will be vital than the height. Do not overcrowd them as they will heat up, suffocate to death, or trample each other.
If you do not want to deal with the hassle of modifying your breeding box, you can go for the Mealworm Breeder Kit that comes with HerpHaven Small Breeder Box, one pound of Mealworm Keeper Bedding, 500 mediums size live mealworms.
It can fit up to 10,000 worms, making it ideal for small scale farming. If you want more, you can get several of these kits.
Secondly, ensure the container is a few inches higher than where the substrate will reach, is smooth to prevent climbing, and has a screen to stop predators, other insects, or animals from getting into this container.
Their common predators include birds, lizards, rodents, spiders, predator beetles. Besides predation, cockroaches, grain moths, flour moths, may join the party.
If you have a plastic container with a lid, cut a hole in the middle section, large enough to allow free air circulation, and cover it with a screen. Afterward, stick a display such as using a hot glue gun while ensuring you can be able to remove and replace the lid that has a screen back.
Alternatively, the fasten or fix the Zilla Fresh Air Terrarium cover onto your keeping container. Note that this screen will ensure there is good hair circulation to keep proper humidity levels, minimize mold growth, and ensure it does not become hot.
Mealworm food and diet – how to feed them
Mealworms require bedding, source of hydration, and gut loading food just before you begin feeding them to your pets or animals to make them very nutritious.
Mealworm substrate or bedding
The mealworm bedding or substrate is what they feed with some of the best mealworms substrates, including cheap homemade ones including oatmeal, wheat bran, cornmeal, wheat grain, and wheat flour.
Other alternatives include uncooked rolled oats, cheerios, fresh oats, Wheaties, dry ground cat or dog food, and so on. If you use chicken or chick feed, ensure you go for non-medicated ones.
Alternatively, there are commercially available mealworm bedding or substrates such as the DC Earth 1LB Wheat Bran Mealworm Bedding made from wheat middlings or Josh’s Frogs Mealworm Bedding or the Fluker’s mealworm bedding.
How do you make their bedding? It is straightforward. Once you have your substrate, fill the substrate in their container to a level of about 2-3 inches and replace the substrate regularly since they eat a lot.
You can cover the substrate for to two thirds with several layers brown packing bags, paper towel or newspaper to give a place for pupating, i.e., they will crawl to them when they want to pupate.
Veggies and fruits food list
For hydration, give them carrots, cabbage, sliced potatoes, kale, lettuce (an excellent calcium source), and apple as well as other fruits and vegetables. Owing to their durability, most people use sliced potatoes as they do not grow molds quickly.
If they don’t get any veggies or fruits for hydration, they survive but reproduce at a much slower pace, something you do not want. Also, there may resort to cannibalism.
While feeding them on fresh food as a source of moisture, ensure their substrate remains dry to avoid molds, fungal growth, or mites.
Additionally, avoid fruits and veggies that quickly ferment, are excessively wet or soggy ones like watermelons since they may make your substrate wet. If wet, it will grow mold. Furthermore, avoid avocado, lemons, cooked veggies, and onions.
Finally, do not provide any water bowl as these larvae will drown. Their source of water is from veggies, the fruits you feed them.
Supplements and gut loading mealworms
Give them nutrition boosting foods such as non-medicated chicken layer pellets, wheat germ, calcium carbonate (ground eggshell powder), soy meal, skimmed milk, dry brewer’s yeast, non-medicated chick starter mash, dry dog food, and a lot of veggies to load them with extra nutrients a week before you begin feeding them to your pets.
Secondly, include soybean meal, what germ, fish flakes, bone meal, graham flour (whole wheat, mouse cubes, Mealworm Chow as they are all good for gut-loading.
Finally, some breeders use food laced with juvenile hormones to make them grow much more prominent and stay longer without molting to pupae. Avoid these hormones if you want to breed them.
Conditions for keeping them
Once they have food, you need to ensure they live at their optimum temperatures and humidity. They do not need lighting. If fact, they love warm dark places.
Although they can thrive in temperatures ranging from 65-100ºF. Their ideal temperature for optimum growth is about 70-75 degrees Fahrenheit.
If you live in cold areas, buy a heat emitter such as Fluker’s Ceramic Heat Emitter for Reptiles, a heat lamp or heating pad, and a thermometer for easy temperature control. Thermometers such as Pangea Digital Reptile Thermometer will serve you well.
A much convenient way to keep the temperature at the required level is by buying a thermostat to help regulate temperature.
Once you have them, strategically place your heating bulb or heat emitter so that it does not dry up the fresh veggies and fruits that may be a source of water.
Keeping the temperature a little higher, such as between 75-80 or up to 90 degrees Fahrenheit will make them more reproductive as it will shorten their pupal stage.
When the temperature goes below 62°F, they will stop reproducing, and if refrigerated at about 45 – 50°F, they become inactive or hibernate. Hibernating them means they will stop growing and or reproducing and sound in case of overproduction.
However, to keep them nourished, remove them from the refrigerator for 1-2 days and place them in their substrate for them to feed. Ensure some fresh veggies and fruits will help keep them hydrated.
Finally, avoid temperatures below 40°F as they are likely to kill these golden yellow grubs.
Ideal relative humidity should be about 50-60%. However, at higher humidity of up to 80%, they lay more eggs.
Although they reproduce more in higher humidity, if it is so high, it will lead to the formation of molds more often as some odor.
In most places, these critters can thrive under normal humidity. However, if they are in a drier area, use a smooth, tall container with water, such as a glass or water bottle, will help keep it higher as they cannot climb on into it and drown.
Finally, you may need a hygrometer such as Exo Terra Terrarium Hygrometer to help you monitor humidity if you live in areas where humidity fluctuates so much.
You do not need any extra lighting as the typical day and night light cycle is enough for them to thrive well. Did you know that these insects love darker places? If not, now you now.
Since they don’t need light, avoid areas with direct sunlight or near windows since they may contribute to a temperature rise making their container to be too warm.
Starting your colony
Once everything is in place, you can begin your mealworm colony. Order your first batch from a reputed vendor. You can start with about 100 mealworms or more. Usually, they deliver them in a substrate, such as wheat bran.
Take older mealworms since they will molt faster to pupae. However, avoid huge ones since breeders use insect hormones to stop them from molting into the pupae stage.
You will take up to 3 months to get your first batch ready, depending on the temperature you put them in and how old your mealworms were when you purchased them.
Care and maintenance
Besides the above, you need to look after your continually after your mealworms and maintain proper hygiene if you want to have a healthy colony. Routine tasks will include:
Check for any dead
Regularly inspect their containers to see if everything is alright. In the case of any dead adult, pupae or larvae mealworm, remove and discard them off as they may grow molds. Your live worms may also eat their dead ones.
Change veggies and fruits regularly
Remove vegetables and fruits after a few days to ensure and add fresh ones. Leaving them for a long time may encourage mold growth or a foul smell (stench) as they begin to rot.
Add more substrate
Since they are big eaters, you need to add more substrate, after a week or two weeks. If they molt, remove the exoskeleton they will leave behind by hand, by sieving their substrate or by the use of cat litter poo scoop.
Sifting frass and remove exoskeletons
Since these larvae molt severally, their exoskeletons may accumulate. If they are not many, you can use a cat litter poo scoop. Otherwise, you should sift them.
Furthermore, there might be a buildup of frass (dusty remains after they have eaten substrate, sometimes known as mealworm casting), which will result in ammonia smell from worm keeper. In such a case, you need to sift them to get rid of all the frass keeping their larvae, pupae, eggs, and adult beetle as well as some of the unconsumed old substrate. Do this about times a year.
The easiest way to sift frass is to buy a set of stackable Sifting Pans, such as the 5-Piece Set of Patented Stackable Sifting Pans. Take 1/2″ , 1/4″, 1/8″, 1/12″, 1/ 20″ and a 1/30″. If you can get a vibration machine, sifting will be made much easier.
Stack these sifting pans from the largest to the smallest and sift the substrate with your worms. Anything you collect after the 1/30″ is frass or mealworm casting, which you can use on your garden as manure or sell as fertilizer.
The rest will be eggs and uneaten substrate, which you can still use. Here is a video to guide you through the sifting process:
After shifting, you can easily remove any exoskeleton and add fresher substrate and return your mealworms, pupae, and back into their container or keep them separately.
When sifting, since the frass is very dusty, you can wear masks and gloves to avoid any chances of you suffering from any allergies.
Finally, letting excessive frass to buildup may result in your mealworms changing color to grey or get gray strips before they die.
Washing the container
After shifting, some people thoroughly clean their meal keeper. Pick any eggs and use a safe, natural disinfectant. A mixture of water and vinegar or melaleuca will work well.
Dry it, put fresh substrate and return larvae, pupae or adult beetles into their container to begin breeding again.
Ensure they do not escape
Since they are pests that can infest stored grains as well as any grain products, ensure they don’t leave their keeper. Usually, this happens when adults lay eggs in grain and grain product containers, and as their grub grows, they feed on these grains. Always have is an escape-proof keeper.
It is not uncommon to get mealworms in the house or your food or beetles, especially where you store your grains, such as the kitchen.
Common problems – fungal infections, grain, and mold mites
High moisture may cause fungal infection, a reason why we advised you to ensure your substrate always remains dry.
Secondly, there might be an infestation of whole-grain mite (Acarus sp.) and mold mites (Tyrophagus sp.), especially from bran or mealworm supplier.
Finally, sterilizing such as freezing or microwaving bran at 130-150F for about 10-15 minutes or going to vendors who do not have these mites, among other ways, may deal with this problem.
Mealworms for sell and success tips
If you intend to sell your mealies, them, typical sizes are ½”, ¾” or 1″ and there are many shipping options either by FedEx or USPS with options such as guaranteed live delivery in winter as well as in fall, spring or summer or with no guarantee.
For success commercially, the best scenario is sizing them small, medium as well as large ones.
For success commercially, the best scenario is sizing them small, medium as well as large ones. Having several containers may help you breed your mealworms more efficiently.
You should separate adults from newly hatches worms as they may prey on them. You should put them in their own container to allow them to breed again while you use or sell their larvae.
Also, at times, giant mealworms may prey on smaller ones or eat pupae, another reason why you may need to keep them separately.
If you want to maximize your profits, invest in giant mealworms. Give them juvenile hormone analog, S-Methoprene, to prevent them from pupating and make them enormous. However, such don’t breed.
Baby, small and mini mealworms
Babies, micro, mini or small are harvested while still young and measure about a quarter an inch. These tiny mealworms are ideal food for smaller pets, including turtles, toads, poison dart frogs, spiderlings, grass finches, and so on. If they are tiny, they may be known as micro mealworms.
Mealworm prices or cost
Their prices will vary depending on their source and size. For instance, the Fluker’s sale 5000 medium size mealworms for $39.50 while Basset’s Cricket Ranch sell 1000 for $13.95 on Amazon with free shipping.
Harvesting and moving your mealworms
Harvesting mealworms can be done with a sifter or by hand. The latter is more tedious. Once you have sifted them, you will have worms mixed with some exoskeleton, substrate, dead materials, beetles, and so on.
You still need to pick the mealworms alone, leaving behind the other stuff. There are various techniques to do so.
The easiest is using egg flats. Place the cardboard inside their container, put some mealworms on top of it, place another egg tray to cover the first one, flip it over, pick the first tray, shake the worms that will have stuck to it to your worm storage container. In case of any beetle, you can remove them manually.
Where to get mealworms on sale
If you are looking for mealworms to buy, you can begin by looking at your local pet store or any farm near you. Once you get them, decide on the size you want and amount from mini or small to medium to large. Buying bulk will be cheaper.
There are many suppliers of mealworms, both the live and dried ones. Popular places include pet stores near you, Amazon.com, PetSmart, Petco, eBay, Walmart, Fluker Farms, Rainbow Mealworms, Mealworms by Pound, Wilko (UK), Tractor Supply (UK), and Home Depot
Other best places to buy mealworms include Tesco, PETstock (Australia), RSPB, Home Bargains, B&M stores, Timberline, Petbarn (Australia), Nature’s Way, Rocky Mountain Mealworms