Starting a mealworm farm is cheap, easy and fun! They are also the favorite treat of my chickens and the wild birds, especially during baby season. Even my husband appreciates them come fishing season. So whether you like giving momma birds a break, have pets that depend on or enjoy them, or like to fish, mealworms can be useful to nearly everyone. Since they are sold at a premium, it makes sense to raise them, and doing so is extremely cheap and low maintenance.
Listen to more helpful tips on raising mealworms in this Backyard Bounty podcast episode!
Table of Contents
What is a mealworm
What are mealworms, exactly? Mealworms are the larval (worm) stage of the Darkling beetle.
They are also the worm found in Tequila!
Darling Beetles, or Tenebrio molitor, are a harmless grain beetles that cannot sting, bite or fly. They prefer dark areas, hence the name “Darkling”.
Darkling beetle life cycle
Darkling beetles reproduce via sexual reproduction. After mating, a female Darkling beetle lays many small, white eggs. In 4-19 days, the eggs will hatch into tiny mealworms. The mealworms grow over a period of time, and the rate of growth is determined by food availability, temperature and humidity.
Once the worms are full grown, they will become pupae. The pupae look like white aliens or mummies. They remain in this state from 2 weeks to 9 months, again determined by environmental conditions, when they finally hatching into white beetles.
As the beetles mature they change from white to brown to black in a matter of a few days. Once they become an adult, they will mate, lay eggs, and the cycle repeats.
As a quick note, I prefer mealworms to Superworms, mostly because superworms bite and mealworms do not. Superworms are also more difficult to breed. There are some advantages to superworms, and they may be more appropriate to your needs.
Setting Up A Mealworm Farm
If you look around online, you will find many systems including rotating breeding trays (also called a Tiered System), nursery trays, etc. This method does work, and results in a higher yield. We raise our mealworms in a tiered system. However for the average user, the simpler one bin method will work great, and with less work.
Although it is a one bin system, I always recommend you have two bins of worms, and I make this recommendation for all worm varieties. This ensures you don’t lose everything in the event that something goes awry in one of the bins.
Here is what you will need:
- Plastic container or aquarium
- Drill or mesh & duct tape (or pop rivet gun)
- Wheat bran or cheap plain oatmeal
- Chicken feed (optional)
- Bucket Sifter
Container or Aquarium
You can choose any plastic or glass container you prefer. The worms/beetles cannot crawl up smooth sides. The two important aspects of the container is that it is at least 4-5” deep (and the wider the better- you want surface area, not depth), and is well ventilated. A dark colored container is also preferable to a clear one, if possible.
You do not have to use a lid, but there is a risk of other creatures getting into your mealworms, like moths or spiders.
I prefer to use stackable plastic drawers, like this. I do not add any lid or mesh to these, and they get enough air flow. Plastic filing boxes also work great.
The bigger the container, the more worms you can raise.
If you use a container with a lid, such as a rubbermaid storage bin, you have two lid options.
You may either drill holes in the lid, or cut out the middle and replace it with mesh or window screen. I caution against drilling holes, as this does not seem to provide enough air flow and there is a high risk of mold which can be fatal to your worms. I speak from experience, unfortunately. This is where having two bins was helpful…
The better option is to cut out the middle of the lid, and cover the hole with screen. You can use metal hardware cloth or window screen. To affix the screen to the bucket you can duct tape it, but a pop rivet works much better.
The mealworm colony lives in a substrate of wheat bran or oatmeal. Although it is commonly called their “bedding”, they actually use this as their only food source and to lay their eggs.
Mealworms cannot live in flour or other fine milled grains, nor can they live in whole grains (like whole or cracked wheat for example).
Take your assembled container and fill it with wheat bran or oatmeal. I use bran, which you should be able to find at your local feed store. If you prefer organic what bran, it is available in our store.
Surface area is more important than depth, so it would be better to have 12”x12” of bran that is 4” deep, than 8”x 8” of bran that is 12” deep.
Substrate should not be more than 8″ deep. Generally the colony will not bury that deep. If they were to go that deep, they are liable to die.
Helpful Hint- It is easier to sift worms from bran than oatmeal
Mealworms are not particularly picky, so don’t stress too much about this. Just make sure you have at least a few inches of bran/oatmeal in the bin, and there is a few inches between the bran to the top of the container.
Just Add Worms
Now that your container and lid (if using one) are ready to go, it is time to add the worms! You can buy them locally, try looking for them in fishing or reptile/pet stores. We recommend Rainbow Mealworms. Either way, I recommend you start with at least 500-1000 worms. The more you start with, the more you can use right away and the quicker the population will grow.
Helpful hint- never buy “giant” or “jumbo” mealworms to start your colony. They are regular mealworms that have been hormonally altered (generally by light exposure to make them grow large but not pupate). Because they are so large, they will never pupate. Once they get old they will just die.
After you add the worms, place a few potato slices or carrots in the container. The mealworms and beetles use this for hydration. Don’t add too many because you don’t want mold or grain mites in your container. I prefer carrots- they last longer than potatoes and are less inclined to mold.
Now it is time for the easy part! Just put the worms in a nice dark spot that’s about room temperature, and let them do their thing. Worms thrive in temperatures of appx 68-80 degrees F and 50-70% humidity.
I store mine in the closet or the water heater room in the garage. If yours are in a dark container, they do not need to be placed in a dark room.
Once mealworms reach full size, they can be harvested. You can either harvest as needed, or batch harvest worms and store them in the fridge. Worms can store in the fridge for several months.
When batch harvesting, store worms in a container with a little bit of bran and a well ventilated lid. Once a week remove the container from the fridge for 24 hours and offer a carrot for hydration. Remove the carrot and place worms back in the fridge.
Helpful Hint- always remember not to harvest too many worms. If you take all the worms, there won’t be any left to turn into beetles. If there are no beetles, there will be no eggs, which means no worms.
Be sure to check your worms every week or two. In a few weeks you should find that some of the mealworms have become pupae. This is good, as you are on your way to a bin that can start reproducing.
When you finally have beetles, I have found it beneficial to add a sprinkling of chicken feed in the bin. The beetles will eat it up! This gives the beetles a variety of vitamins and minerals, and prevents them from eating eggs or young mealworms.
Make sure there is always a few inches of substrate in the container and add more as needed.
Helpful Hint- If you use chicken food, check the tag and make sure it does not contain diatomaceous earth. Many feed producers add DE to prevent pests in the feed, however it will slowly kill your entire colony.
Depending on the size of your bin, eventually you will find that the wheat bran has been replaced with a dark sand like material. This is called frass, and simply put, is mealworm poop. A few times a year you will have to sift the worms and beetles out of the bin, throw out the frass, and refill the bin with wheat bran. Try not to do this more than necessary however, as you will also be throwing out small baby worms and eggs. I throw the frass in my chicken coop and let them scratch through and find any worms I’ve missed. A mesh strainer from the dollar store will work to sift them out, but this bucket sieve set works much better.
Helpful Hint- Save old frass in a spare container for 1-2 months and see if any baby worms are inside. You’ll probably be surprised, frass is often filled with eggs! Hand separate or sift baby worms and then use frass in your garden. It makes an excellent balanced houseplant or garden fertilizer!
You will also have to periodically remove the sheddings that accumulate on the top of the bin. I simply take the bin outside and wave the lid over the top, using the air movement to blow them out.
Mold is caused by either overfeeding, poor ventilation, or both. Either feed less or change to a different top to prevent it from happening again.
If you find mold in your bin, immediately open the top and let it air out. Sift out as many worms and beetles as you can, and throw out all of the bran. Before you add new bran to the container, clean it out with a diluted bleach water mix to destroy the mold spores. Rinse well and allow to dry. Finally, when you re add the bran and worms, try not to add any of the moldy bran that might be mixed in with the worms.
Grain mites are the result of prolonged moist bedding.
Most substrate naturally contains grain mite eggs, it’s essentially unavoidable. You will read many articles that suggest baking your bran at 200 degrees F for 20 minutes before using to reduce chance of grain mites. Unfortunately this is not effective in killing the grain mites.
The single best way to prevent grain mites is to only give your colony enough potato slices or carrots for one day. If they still have some at the end of the day, take them out of your colony. Wait a day or two between offerings.
By removing the hydration source, the substrate cannot absorb too much water. It is the moist bedding that causes the mite eggs to hatch and their population explode.
If you do over hydrate and end up with grain mites, simply remove damp bedding and wait a week or so before offering hydration. Going forth be more vigilant about reducing substrate moisture.
Temperature and humidity problems
You want your colony to stay warm, but not too warm. Temperatures below 68 degrees can cause them to cease reproduction, and over 80 degrees can be fatal. Try moving the colony around until you find a stable, warm place in your house. Do not place them in direct sunlight.
If you live in a very dry environment, you can increase the humidity in your colony by placing a shallow container with a bit of water and sponge on top of the substrate. Make sure you don’t spill any on the substrate, and that the container has plenty of ventilation.
I want to raise mealworms, but I think they are gross!
Beetles and worms cannot bite, and beetles cannot fly. The worms do wiggle about when picked up, and have a pointy “tail”. They may poke you with their tail in an attempt to get away, which the squeamish may mistake for being bitten, but can cause no harm.
If you don’t want to touch them, you can use a spoon to pick them up. Family members, especially children, may also be willing to help. In time you will get used to them.
And that’s about it! If you have any questions or comments, feel free to comment below! As always, we thank you for reading!