Breeding Mealworms

I see so many questions on many different forums asking about breeding mealworms; and though there are many websites online that explain the process, I thought I’d make an instructional guide myself. I’d like to mention that there are several ways of doing pretty much anything, and there’s no exception when it comes to breeding mealworms. This is the way I’ve done it, and has worked for me. Others may wish to change enclosure sizes, types, etc. which of course is ok.

Mealworms are the larvae stage of the Tenebrio Molitor, the Darkling Beetle. It isn’t the mealworm itself that breeds, it’s the Darkling Beetle. There are four stages to a Tenebrio Molitor’s life. Those stages are of course, first, the egg. These then hatch into very tiny mealworms. These mealworms grow to be about an inch in a month or two. These then pupate, which look like alien-type curled up mealworms. Once they emerge from the pupae, they’re at the final stage of life. The stage that does the breeding, which is the beetle. The mealworm’s life from the day the egg is laid to its death can be approximately 5 months or so.

In order to start a colony, you’ll need the following items.

• 2-3 medium-large (15+ qt.) plastic containers/shoe boxes - Wal-Mart, $1-$6 depending on size.
• 1 small plastic container/shoe box (5 qt.) - Wal-Mart, $1
• Wheat bran - Feed store, $10 for 20 lb. bag
• 500+ mealworms - Online or pet store (Petco 500 for $6.99)
• Fruit or vegetable for water source - Potato, carrot, apple, etc...

All containers should be cleaned and washed prior to starting a colony as you don’t know exactly where it’s been. Once this is done, place about 2 inches of bedding in one of the bigger containers. This is where you place your mealworms. You can of course start with a smaller amount, and use smaller containers, but this is what I use. You can use several smaller boxes for groups of smaller colonies, or you may use several big boxes for one big colony. Your choice. I’ve also heard others that don’t move the different stages into different boxes and just breed in one large container. I move mine just to be on the safe side.

In a bed of bran, the mealworms grow and molt very quickly. Depending on the size of the mealworms you’ve purchased, it can take from 1 week to a month or so for your mealworms to pupate. This is why it’s suggested you purchase the largest mealworm size available. Do not confuse regular (Tenebrio Molitor) mealworms with Superworms or Giant Mealworms. Giant Mealworms have been fed a growth hormone that sterilizes them, leaving them infertile. Most say that they don’t pupate at all, which I find untrue as I’ve had many pupate on me, though I have yet to see any hatching mealworms from that colony. Though they look similar, Superworms are NOT Tenebrio Molitor and are a completely different species (Zophobas Morio) than the mealworms we’re breeding here.

You may place carrots, potatoes, apples or your choice of moisture on top of the bedding. If there is not enough moisture in the bin, they may cannibalize each other. But, too much moisture and the mealworms may die from molding. It may take trial and error to find out how much to use. I place about 3-4 1 1/2 inch carrots in mine and change it every 3 days once they’ve dried out. I don’t believe apples work as great as it molds VERY quickly.

Here is what the pupae will look like:

Here is what the beetles will look like a few hours after emerging from pupae:

Once the mealworms pupate, they can be removed from this container into a smaller container with only an inch or less of bran. I use a 5 qt. shoe box, but any other would work. They don’t move much if at all at this stage, so size of the box doesn’t really matter. They’ll stay in the pupae stage for approximately 2 weeks. I don’t put any sort of moisture in this bin as once they turn into beetles, I remove them quickly into the next container.

Once they turn into beetles, it is best to move them quickly to the other large container, which is their breeding container. If left with the pupae, they may cannibalize and kill the pupae. In this container, there should be 2" or so of bran. They will start breeding in the first few days once they’ve become beetles, and will continue until they die. I haven’t quite noticed when and how often they die, but I’ve heard ranges from 6 weeks, all the way up to 16 weeks. Many do agree though that a female will lay between 200-500 or more eggs in her lifetime. Given the big range of its lifetime, I’d say that’s an approximate 100 eggs you should get from one female every month. This container should be supplied with moisture as well. I also put about 3-4 1 1/2" pieces of carrot in this bin.

This is what the beetle looks like in their color stages - The lightest just molted from a pupae, the next darkest is about a day after, and the darkest is what it looks like when it's fully a beetle:

This is a good size starter colony with about 150 beetles:

I personally move the beetles every 2-3 weeks into a new container with new bran to avoid the beetles eating the eggs. I believe this gives you a better rate of surviving mealworms. The old bedding I then put into a 16 qt. container to grow out. You can put it in the same container as the larger mealworms but I like to keep these babies separate. Once they grow a bit, I then put them with the adults. Again, you don’t have to do this. This is just what I do.

In a month or so, you’ll start noticing a whitish/light grey powdery substance in your mealworm bins. This is frass (mealworm poop). Once there is a noticably larger amount of frass than bedding, they bedding should be changed. This isn’t necessary in the breeding bin, as this is always changed and put aside every 2-3 weeks anyway.

With a starting amount of 500-1000, you should yield a good amount of beetles to start with a good size colony.

Here is your outcome: