Materials and supplies
- A plastic container with smooth (unscuffed) sides so the mealworms can’t climb out. A lid is optional. A screen or large piece of mesh cloth to allow airflow and keep out pests is better. The large, 1 lb. salad containers from Costco are the perfect size for up to 2000 mealworms. Try not to crowd your worms too much as this can result in excess death. Cost: $0
- Grain for the bedding and food source. Some peolple use wheat bran, cornmeal, or rolled oats. I use regular rolled oats since that’s what I have on hand. You’ll want to fill your plastic container about 1″ deep, no more. Bedding that’s too deep can cause overheating as mealworms generate a lot of body heat. I ended up filling the container with about 4 oz. of oatmeal. Cost: $0.20
- Some place warm to keep your worms. You’ll want to find somewhere that’s at least 80F, but under 100F. Do not leave your worms out in direct sunlight during the summer unless you want to kill them all!
- Some paper towels, scrap cardboard, or newspaper for the larvae to crawl under. Cost: $0
- A plastic water bottle or small container to hold the pupa so they don’t get munched on by the worms. Cost $0
- Mealworms! I got mine from Rainbow Mealworms on Amazon. You can buy them directly from Rainbow Mealworms’s website, but I prefer Amazon for the buyer protection especially with something like mealworms that could arrive dead at the post office. You’ll want at least 1000 mealworms for a faster start to your colony. Cost: $15
Housing your colony
Prepare your mealworm container by sterilizing it and making sure that it’s 100% dry.
Next, you’ll need to prepare the bedding. Do not skip this step! You’ll want to kill all the grain mites that are in the grains. Grain mites are tiny dust like mites that are almost invisible to the naked eye until they gather in large clumps. They are found in almost all grains, even those meant for human consumption.
Take your oats, wheat bran, corn meal, whatever, and either nuke it in the microwave for about a minute (open the door and check the grains constantly to be sure you’re not burning it) or freeze the grains for at least 3 days.
Humid environments (like a mealworm colony with wet vegetables) is the perfect environment for a grain mite infestation. Grain mites are not an immediate killer of mealworm colonies, but they do compete for food and they can prey on mealworms that are shedding their skins.
Fill your plastic tub with about 1″ of the clean grain. You’ll only need this much at any time. A bedding layer that’s too deep can cause overheating and excess deaths in your colony.
On top of your grains you’ll want to add some pieces of cardboard or newspaper for the worms to hide under. Remember, they’re calle darkling beetles for a reason–they like to hide in dark places. Cardboard pieces are also a great way to take out any worms for feeding your chickens. The worms will cling onto the underside of the cardboard and you can just flick them off onto the ground for your chooks.
If you have problems keeping your colony humid, then you might want to place a lid on top of your container. Otherwise, some light cloth or wire mesh is the best choice as it allows airflow, preventing problems with mold and mites.
I used to use a lid to protect my mealworms from the super dry air where I live, but after a while I started having problems with mold and grain mites. I switched to covering the containers with light mesh cloth and instead top up the container with wet paper towels once in the evening and once at night. So far there have been no more problems with mold or mites.
Feeding your colony
Since the grain based bedding also acts as a food source, you really don’t have to feed your worms anything else. Some people give a protein source such as dog food or chicken feed, but I find that these extra food sources grow moldy very easily so I skip this step entirely. You can also load your mealworms with nutritional yeast a day or two before you feed them to your chickens. The yeast will make your worms grow fat and juicy and it’s an easy way to load your worms with extra nutrition for your chickens. I prefer just adding the nutritional yeast to my chickens’ wet food.
The most important thing you need to provide your mealworms is moisture. Mealworms don’t drink water, but instead get their moisture from eating things like vegetable and fruit scraps and moist pieces of paper. All you have to do to maintain a healthy colony is to make sure they always have a source of moisture available. If you live somewhere humid, you may only have to add scraps once a week. I live in the desert so I have to add scraps or moist paper to the colony once in the morning and once at night.
How long does it take to get a productive colony growing?
How fast your colony of mealworms grows depends on the number of mealworms you start with, the temperature of the rearing container, and the humidity of the container. This can vary from as fast as 8-10 weeks during the summer for the entire cycle from egg to larva to pupa to beetle, or as long as 5+ months in cold weather.
Here’s how long it took for us to get our colony started from the time we received our shipment of mealworms.
- 6/7/2016: order placed for 1000 small (1/2″) mealworms.
- 6/11/2016: picked up mealworms from the post office. The mealworms were packed in crumpled newspaper inside a mesh bag. We could hear them slithering and rustling about inside the box while we were in the car–kinda gross and creepy! When we got home I had to unpack the worms and shake them out of the newspaper. Make sure you do this step outside on the patio or driveway and bring a large pan with you to contain the mealworms, they crawl really fast and they will escape everywhere. The sizes were a mix ranging from over 1/2″ to as small as 1/4″. There were very little deaths, under 10 dead worms, even though temperatures were in the high 90s.
- 7/4/2016: found our first pupae, 2 of them to be exact. 24 days after receiving our shipment. At this point I wasn’t keeping the worms on top of my LED shop light, so the temperature of the container was the same as room temperature (79F-82F). This is a bit on the low side and it explains why it took so long for the mealworms to pupate.
- 7/10/2016: found our first beetle. It took one day for the beetle to turn caramel brown and two more days before it was completely black.
- 7/20/2016: we’ve got our first eggs and the beginning of our second generation of mealworms! I noticed that the eggs were drying out so at this point I started placing damp paper towels inside the breeding container.
- 7/27/2016 (2nd generation): first baby mealworms hatched! At this point we’ve relocated the rearing bin to the top of our LED light. The temperature of the container is now 90F-96F.
- 9/20/2016 (2nd generation): first pupa sighted.
- 9/24/2016 (2nd generation): first beetles emerged.
- 10/2/2016 (3rd generation): first eggs laid.
As you can see, the 2nd generation which we raised ourselves was completed in just 75 days. It took the larvae 56 days to grow from new hatchlings to pupae.
The mealworm life cycle: from egg to larva to pupa to beetle and back to egg. How to care for your colony.
I’m not going to go through and explain each stage of the mealworm’s life cycle as you can google that yourself, but just know that mealworms are the larvae of the darkling beetle and that it’s the beetle that lays the eggs which hatch into worms.
The in between state from worm to beetle is called a pupa. These little guys are basically mummified and stuck until they mature and emerge as a beetle. I think these pod-guys look like Kakuna (the pokemon) and always call them kakunas instead of pupae!
There are many schools of thought on whether each stage of the mealworm’s life cycle should be separated out. Some people keep all stages separate from each other, while others only separate out the pupae and beetles.
Some people set up complicated sorting systems and multi-tiered bins, but I like to keep it simple and keep everything in one bin. That doesn’t mean that I don’t separate the different forms.
The most important thing to do is to keep the pupae separated from the worms and beetles as they’ll eat the poor pupa if you don’t have enough moisture available in the bin. Whenever I notice pupae starting to appear on top of the oats I scoop them up with a spoon and deposit them into an empty water bottle that I keep inside the worm bin. I do this once in the morning and once in the evening when I add veggie scraps to my bin. The one time I forgot to check for pupae in the morning because I was too busy resulted in finding two empty pupa shells in the evening with a giant hole gnawed out of their torsos. 🙁
Besides separating out the pupa, you may want to separate out the beetles into another container. This step isn’t necessary, but I like to do this so that I can see how many eggs the beetles are laying and so that the eggs and tiny newly hatched larvae aren’t mixed up with all the frass and dust in the main mealworm bin. Mixing eggs and tiny larvae in the main bin means that you won’t be able to sift out the frass from your main worm bin.
And yes, you should sift out the frass (bug poop) and dust that accumulates under your layer of grains. The build up not only smells, but the frass actually contains a chemical that can keep your mealworms from pupating (turning into pupa). Your worms would just get bigger and bigger, but never maturing into the next stage in their life cycle. This chemical is actually what’s used to create giant mealworms (sometimes mistakenly called superworms).
I clean out the frass by sifting everything through a kitchen strainer once the frass gets about 1″ deep. If you have very tiny worms in your colony, make sure to poke through the sifted frass to see if any mealworms slipped through!
Mealworm eggs are tiny! Here’s a photo of a beetle actively laying an egg on a piece of cardboard. You can see the beetle’s ovipositor sticking out as it tries to deposit the egg. Each female beetle can lay hundreds and up to thousands of eggs over a couple months. The best way to increase their laying rate is to keep temperatures high and humidity levels up. If you keep the beetles in a separate container, you’ll see the beetles lay less and less eggs as they get older. At that point you can feed the beetles to your chickens!
Eggs take about 2 weeks to hatch and the newly hatched worms are tiny, white, and very hard to see with the naked eye. You’ll want to avoid moving or poking the eggs because they’ll just explode into a gooey mess. If any eggs are stuck to the container, just leave them there until it hatches!
How can I get my mealworms to grow and pupate faster?
The key factors to fast growing worms is temperature and humidity. The ideal temperature is around 82F-95F and the humidity in your bin should be at least 50% relative humidity. While it is possible to keep your worms in a colder room with temperatures in the seventies, this will slow down their growth and extend the larvae stage from weeks to possibly months.
I keep my worm bin warm by placing it on top of the LED shop light I use for my indoor garden. Another good place to keep your worms warm is next to your water heater, on top of your refrigerator, or on top of your desktop computer. You can also use a warming pad, but I’m a cheapskate who thinks that’s a waste of electricity.
As for maintaining the perfect level of humidity, you’ll want to have enough sources of moisture for your worms so that the smaller baby worms don’t dry out. Mealworms also need enough moisture so that they can store enough water to successfully pupate, but you don’t want the bin to be so wet that the bedding starts to mold.
If your bin is too dry or too wet, you’ll start to see dead worms in your bin. Dead worms are easy to tell apart since they’ll turn into a black shriveled husk.
Keep in mind that I live in the desert where the relative humidity hovers around 5% – 15%. If I still lived in the mid-west where the relative humidity is usually around 60%-90%, the methods and materials that I use for giving the worms moisture would be different. You’ll need to experiment to find the perfect solution for your local environment.
The worst moisture sources
- Apples or fruit of any kind – the fruit pulp dries up and turns gummy, killing any worms that get stuck inside.
- Potatoes and sweet potatoes – again, the potato turns gummy as it dries and traps worms inside
- Tomatoes and cucumbers – too wet, causes problems with mold
- Kale – Dries too quickly.
The best materials for adding moisture to your mealworm bin
All of these sources dry nicely without molding or any messy residue and the mealworms easily burrow through the vegetables without getting trapped.
- Brocolli stems
- Cabbage leaves and stems
- Celery leaves and ends
- Carrot ends
- Asparagus stalks – by this I mean the tough woody ends that we break off and throw away. I had to slice these in half because the outer layer was too tough for the mealworms to munch through.
- Folded toilet paper or napkins misted with water daily – I use this when I don’t have enough vegetable scraps on hand to feed to the worms. I have to fold the paper into thick wads or else they dry too quickly. If you live somewhere that’s more humid (not a desert!) then you may have better luck covering your bin with a thin layer of unfolded moistened paper.