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Mealworms

Last Updated: 11/8/13

Raising a Perpetual Supply of Mealworms!

From top to bottom are a small regular mealworm larvae (1), an adult black regular mealworm beetle (2), a just-out brown adult regular mealworm beetle (9), a regular mealworm pupae (5), a giant mealworm pupae (4), an adult king mealworm beetle (3), a large regular mealworm larvae (6), a giant mealworm larvae (7), and a king mealworm (8).

Animals that Eat Mealworms
Mealworm Setups
Feeding and Watering
Breeding
Maintenance
Grain Mites
Links

I decided to create this page once I started keeping masses of various mealworms to keep my Sonic and Miss Prickles happy! They were African pygmy hedgehogs. I already kept mealworms for my chickens and sailfin lizard.

Let me know if there is any information that you think I should include on this page to help provide information to others!

Also, see my page on caring for crickets if you have them.

There is also a page on controlling ants without killing your mealworms.


Animals that Eat Mealworms

There are three kinds of mealworms I find available. The smaller animals need young mealworms. The larger the animal, the further down this list they can go for food choices. The first two kinds rarely bite but the king mealworm may bite so only give it to animals that can "handle" them, mostly larger lizards and birds.

R = regular mealworms
G = giant mealworms
K = king mealworms, also called superworms or megaworms

The following are some of the animals that will eat mealworms.

Birds:
Chickens, turkeys, guinea fowl, peafowl, quail, chukar, pheasant, bluebirds, songbirds, and well most birds!

Mammals:
Hedgehogs (mine loved the adult mealworm beetles too!), shrews, moles, voles, bats, rats, and other mammals that eat insects.

Reptiles:
Aquatic turtles of all sorts, box turtles, tortoises, sailfin lizards, chameleons, fringe-toed lizards, basilisks, water dragons, basilisks, anoles, and well most reptiles that eat bugs!

Amphibians:
Frogs, toads, newts, and salamanders of all sorts!

Fish:
Archers, goldfish, piranha, arrowana, and any big fish that eats bug meat!

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Here is a question often posed:

Do I have to cut the heads off of the mealworms before feeding them to my animal. I've heard they will bite them internally?

Well, yes and no. If an animal consumes a king mealworm without killing it (by chewing), then it may bite them inside their stomach. This has happened to less-than-intelligent human beings. Regular mealworms are simply too small to pose much of a risk as the acid in the stomach and the trauma of being eaten will probably disable them anyway. Most animals do chew their mealworms including basically all of the above mentioned animals with the exception of some fish and birds. Now, let's think how things are done in the wild. Do wild birds have a caretaker chop the heads off of their bug prey before eating them? I think not. My chickens swallow live regular mealworms whole without chewing and none have chewed their way out yet! It is simply not very comfy down inside most animals digestive systems so mealworms do not have much of a chance. I only suggest cutting the heads off or otherwise killing the mealworms before feeding if you (or another human) are eating them yourself and planning to swallow them whole, or you are feeding them to a non-masticating (an animal that will not chew it but swallow whole) ill animal. Healthy animals should have no problem. Again, in cases where you hear about mealworms chewing from the inside, it is usually referring to the king mealworms.


Mealworm Setups

Regular and giant mealworms can be stored in the refrigerator to prevent pupation. They will eat almost nothing in that state and live longer in a sort of hibernation. King mealworms will die in the refrigerator. I do NOT refrigerate mealworms that I get as I consider it cruel to deprive them of the things they love to do: eat, drink, run around, and pupate to later breed. In the refrigerator, they are in a sort of stasis. Those mealworms have a lot less nutrition than plump, well-fed, happy mealworms kept at room temperature. Feeding them is called "gut loading." If I feed them good foods, then the chickens, turtles, and hedgehogs who eat them will in turn be eating those foods that are inside the mealworms.

I use plastic containers sold to hold fish and other small animals that do not belong in such small homes. These homes are fine for mealworms though as they are much smaller. Sizes from a half to two gallons are best, depending on the number you want to keep. For a breeding colony, you will need at least two containers (adults and larvae) with three being even better (adults, newborns, and larger larvae used for feeding). The lids have holes all over them.

You can also use any plastic or glass container. It MUST have multiple air holes, with a mesh lid even better. Mealworms will die off if they do not get enough circulation. I have tried using plastic ice cream tubs with holes punched in the lid but they always died off after a week or two because there was just not enough air getting in there. For huge cultures, using a big under-bed plastic storage tub works well. Also, aquariums work well. You can leave the lid totally off if you do not have other animals that will go playing in it. We have cats so, if we did that, they would probably use it as a litter pan!

Kept in too small containers, mealworms will die, and/or you will have to clean up often.

Mealworms should be kept out of direct light but not be kept in total darkness either. I put my containers under my lizard's 120 gallon aquarium, in the cabinet. Later, I moved them to the basement after ants took over. Keep them in an area with some ventilation and subdued lighting.


Feeding and Watering

Foods that I offer my mealworms (both larvae and adult beetles!):

King mealworms like a carrot to bore into.

Water:

To provide water for the mealworms, I soak a paper towel and ring it out most of the way. I put a new one in the container every other day. If you have more mealworms, add more paper towels and add new ones daily. I leave the old, dry ones in until I clean the cages on Saturday morning. If you provide water in a dish, they will drown and make a mess. You can try to rely instead on wet sponges, fruits and vegetables with high water contents, or "cricket quencher" which is a polymer that insects can suck water out of. Without water, mealworms will die shortly. There are insect "water pillows" they are selling which you wet, and they retain water for the insects to drink. I have been using them for my crickets but have not put any with the mealworms who seem to enjoy to crawl in the paper towels more than anything.

On 11/1/04, someone e-mailed and asked about my mealworm setup and feeding so this is a copy of my response to their e-mail which covers a number of things:

"I've found that mealworms will mix everything up anyhow no matter where I put the various foods or wet paper towels. They all end up well mixed in a few days. So, I put them in the cereal such that the mealworms can bury into it some. I don't make it very deep. They usually like going up into the paper towels so by the end of a week, most of the cereal is gone. I then shake them in a colander to remove the uneaten food and poo. I also have these yucky mini mites that can barely be seen living in my animal containers now so I'm trying to remove them when cleaning. Anyway, the cereal is sort of a bedding. On top of that, I put some fruits and veggies every other day and the wet paper towel which I try to put on a bare spot to reduce rotting the food (and those weird bugs like wet food). It probably doesn't matter if you mix in other foods or not, since they'll move things around. If they're not, they may have too much substrate. I feed my bugs (crickets, mealworms, etc.) human baby oatmeal cereal and ESU gutload food so they should get enough vitamins and minerals. Plain bran may not have the right mix of vitamins that you need if you're relying on raising them up/increasing their size. Most people keep mealworms in the fridge and don't even feed them (they're in bran but don't eat much when cold). Mine are fed well. Of course, that means dealing with pupae, adult beetles, and then more baby mealworms. But, that does give a variety to what's available. My chickens like to eat pupae and my hedgehogs loved the adult beetles (crunchy!)."

The mini animals looked like white mites. I had yet to put one under the microscope because they give me the creeps. I finally did that on 12/24/04. They are indeed eight-legged white mites. They are in my insect cages in massive numbers so that the substrate moves. Plus, they let off some sort of stench! Does anyone know what they are or how to get rid of them and not kill the feeder insects in the process? They are really bad in my baby mealworm setup so every once in a while, I have to dump it with the mealworms that are too small to sort out. I always feel bad.

I got a response to my above query. See the section on grain mites.


Breeding

You may wish to breed mealworms so that you can grow more larval mealworms, grow beetles to feed certain animals (like hedgehogs and small reptiles) for variety, or go grow the very tiny young mealworms for smaller animals. You simply cannot buy two-week-old mealworms for a hatchling snapping turtle for example. You have to raise them yourself.

It is very easy to get mealworm larvae to pupate, in fact, you cannot stop it unless you refrigerate them. When a few months old depending on temperature and feeding, mealworms will pupate. The pupae are yellowish white and wiggle when touched. I remove these to the adult beetle enclosure weekly. The adults are very active and will lay eggs in cork bark and oatmeal as well as other substrates that are grain or wood based. They may also like to lay eggs on strips of paper, newspaper, paper towel, etc. on the surface of their substrate. Remove the substrate (or paper if you are using that) weekly to the baby container to grow out the babies. They are almost impossible to see when newborn but will grow to be completely visible in a week. The warmer it is, the more they eat, and the faster they grow.

King Mealworms:

An upside-down king mealworm pupae on 11/20/04.

My setup for breeding king mealworms. You can see a few adult beetles in there. At the time of this photo on 11/20/04, there were about 10 adult king mealworm beetles I put in the one gallon container with reptile bark substrate. After leaving them for about three weeks, I will remove them and then raise another batch of larvae. I had done this once before and yielded a few hundred king mealworms which are now getting large enough to feed to my lizard after four months of growth.

This section was copied from my sailfin lizard care page except for the last paragraph which I added later (here only).

Occasionally, one of my king mealworms will pupate into a beetle. I had a male beetle for almost a year before another beetle developed. These two beetles did mate (I witnessed this; the male's apparatus protrudes) but the female either did not lay, or I tossed the eggs out during the weekly cleanings. The male died soon after mating (he was a year old). I had not previously had any luck getting baby mealworms until I read to use cork bark on which for them to lay. I began collecting rolled up king mealworms when I cleaned Einy's cage. They pupated, and I soon had about six adult beetles. They were put in a 2 gallon plastic cage with egg crate, damp paper towels, food, and a piece of cork bark. Every week, I checked the bottom for any sign of life. Finally, I began seeing itty bitty worms. I poured them into a 1 gallon plastic cage and put in a generous helping of cricket food (basically oatmeal and such). They hid and ate and grew bigger and bigger. After a few months, some became large enough to pick up.

You will note that I did one thing very different from the typical method for breeding. I did not put the larvae (big worms) into individual containers and cool them or otherwise try to induce them to pupate. I simply fed them very well, provided wet paper towels (changed every two days), and put them into the lizard's tank. As she did not eat them all, some bore into a log I had in with the lizard and chewed some wood. Then, they hid in a dark spot under the rug or behind the log and rolled up. I used to think these rolled up worms were dead! Then, I finally realized they were in the first stage of pupation (they will NOT move then). Once white pupae, they do wiggle if you touch them. I put any rolled up mealworms or pupae in with the other beetles. After a few weeks (temperature dependant), the beetles emerge. I have yet to see that moment for a king mealworm but have for regular mealworms! The newly emerged beetles are brown/white and soft. After a few days, they turn totally black and hard.

Update: By late 2001, I now have plenty of adult king mealworms in with a ton of adult regular mealworms. There are a lot of beetles! Weekly, I dump all the uneaten feed into my baby container. Eggs and newborns are in the floor debris. Since it is hard to see them, I just put it all into the container. The baby cage is crawling with mealworms of all sizes but mostly the regular mealworms. I still have to buy king mealworms every once in a while.

In July of 2004, I finally came up with a better way to get baby king mealworms. When mixing them with the regular mealworms, I almost never got the king mealworms to result. Plus, these white thing bugs were in there that make the cereal mushy and stinky. I do not know what they are but they are gross (they were grain mites). They are too small to even count the legs or anything. Maybe one day I will put one under a microscope. Anyway, I put about 9 adult king mealworm beetles into a half gallon container with an inch or reptile bark as well as some food and a wet paper towel. I left them in there for three weeks. Then, I removed them. Lo and behold, I then had a colony of their babies. While a few of those gross bugs were indeed in there too (do not ask me how!), it was a little cleaner with the bark. I of course could not sift anything and had to wait for the babies to grow up which took a long time. The beetles liked to lay their eggs in bark or other wood products. I also put the king mealworm pupae in there with the tiny larvae since the adult beetles of both kinds (and probably the large larvae) tend to eat them! When one turned into an adult, I moved it with the others.


Maintenance

Run the mealworms, food, etc. through a colander. The mealworms should stay in the top with the food, litter, waste, baby mealworms, etc. going to the bottom. If you have babies, save the "waste" in the bottom in another container. If they are larger babies, and you have the time, you can hand pick them out using a small spoon. I can use my fingers for small mealworms but if they are too small, they get squished.

Clean the containers weekly by pouring the larvae into something else and cleaning the cage. Add new wet paper towels every few days but it depends on how many mealworms that you have. Remove dead insects (no matter the stage). Some people feed dead insects but I never do as, once they start to decompose, they may contain harmful bacteria, fungus, etc. You never know why one mealworm might die. Dead larvae turn black. Dead pupae turn brown and shrivel up. Dead beetles that die early are deformed while ones that lived out their lives, simply look the same but stop moving, and their antennae crinkle up. They will not move. Adult beetles always move when touched. They exude a chemical similar to formic acid with ants. You will be able to smell this when you disturb the beetles. It is nothing to worry about but something to note.

To separate the larvae from the pupae and adults, I use my fingers to hand pick out the adults and pupae. The pupae wiggle but cannot get away while the beetles will try to get away. If you do not want to touch them, try a small cup to pick up the pupae and adults.

Eventually, the cereal or substrate will be more feces, urine, dead insects, shriveled up veggies, etc. than substrate anymore. At that point, run the larvae through a sifter to catch everything large. Then, go through the stuff that went through the sifter to find tiny larvae if you are breeding them. The ones that are too small to pick up, use a spoon. You will not get them all so some may have to be thrown away to be able to change the substrate 100%. If you do not ever change the cereal substrate, it will rot, stink, and grow white and green fungus (and grain mites) and kill the mealworms.


Grain Mites

My baby mealworm containers had these tiny little stinky white mites. In response to my question about them above, I got this message from Franz on 2/14/05 and 2/15/05. I have corrected spelling and grammar in the following quote.

"...Your mealworms are infested with Grain Mites (Acarus sp.). At the high humidity your wet towels provide, these parasites flourish. They are prolific breeders (800 eggs per adult female) and have a life spawn of about 17 days. The eggs can withstand temperatures of 0 degrees for months and still hatch when brought to room temp. The adults feed on embryo seed which is the reason most mealworm growers usually use hulls. The larvae have a period where they can become dormant and resist most insecticides, heat, drought, starvation. They are kind of a super insect. Pretty common. The only way I have heard of removing them is tossing the entire culture and starting fresh....By 'hulls,' I mean wheat middlings. They are the byproduct of wheat flour processing and actually contain a surprising amount of nutrients. Most mealworm distributers will sell in bulk. I have used www.wormman.com for the bedding. I throw in a little cricket food and herp vitamins in my bedding. For moisture, I use carrots, potatoes, and apple slices. I would suggest cleaning your bins with a white vinegar wash followed by a rinse with hydrogen peroxide. Your standard grocery store varieties should work...." I want to note that the mites are not true parasites, and they are also not insects. They are arachnids. As a chemist, I can vouch that the store bought vinegar (acetic acid) and hydrogen peroxide (H2O2) are the same thing as the ones at the lab except for the concentration. They will disinfect pretty well. Personally, I use bleach to clean out all my various animal containers, bowls, etc.

On 10/7/05, Richard sent me the following advice:
"In order to keep the substrate of my mealworm and beetle breeding colonies dry and so mite and mold free I place a piece of cardboard or folded brown paper on the top. I then place fresh non-citrous fruit and/or vegetables on top of the cardboard/paper, which are replaced daily or at most every other day so as to avoid the build up of dangerous pathogens - I've no idea if pathogens really are a problem, it's just some advice I was given. Beetles like to congregate underneath the paper/card whilst mealies like to nestle between the paper folds. I only use human-grade supermarket own-brand wheat bran and rolled oat flakes as a substrate as I've heard reports that the cheaper animal feeds often harbour the grain mite."

On 1/26/07, Ginny sent me the following advice:
"One local lady told me the grain mites are killed by microwaving the bran first which kills off the mites, and it is then safe for the grubs. There doesn't appear to be any remedy for getting rid of them once the grubs are infested though. Thought I would pass it on to you. As the bran I use is all stock feed quality it is probably loaded with the mites so I intend to use it as my first line of defense."

On 3/14/07, Cate sent this advice. She is from Australia as was Ginny above. Cate said to use wormwood. When I asked about wormwood, she said: "Wormwood (Artermisia absinthium) is a herb that has psychoactive and hallucinogenic properties. Wormwood is said to affect the neuro receptors in the brain in a similar way to THC (the psychoactive component present in cannabis). They also use the herb to make the alcohol called absinth. In the states, I believe it is legal in some states but should be freely available from any plant nursery as it is a herb. The plant comes in 10 inch pots here, and it's a rather bushy little plant, and they cost around $20.00 Aussie for each plant. You only need a few leaves in each worm container. My worms are in 35 litre containers and all I used is half a dozen sprigs in each, and, as it dries in the bran, it concentrates. I replace the leaves once a month."

Amy let me know on 2/15/09 about this source for dried wormwood leaf:
DragonMarsh


Links

Breeding king mealworms - this is an archived version of the site as it no longer exists.

Raising Live Feeder Foods - this is an archived version of the site as it no longer exists.

Worm Man - sells live crickets, mealworms, king mealworms, butterworms, etc.

Mealworm discussion in my forum

Raise your own mealworms - a thread on a board about mealworms that I found since they mention my site. They have a lot of photos. This is an archived version of the site as it no longer exists.

Topflight Mealworms - sells mealworms.


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