Random Bits of Projects

August 4, 2008

How to Raise Meal Worms

Update May 15, 2009: I added a quick note on raising a smaller amount of worms at the very end as well as a precaution against moths and mites.

Meal worms are handy for feeding a variety of animals. I feed meal worms to my fish and to wild birds at outside bird feeders. Other people use them to feed pet reptiles, skunks, sugar gliders, and so on. If you use very many, it can get expensive buying them from a pet shop or wild bird store. Raising them is an easy option not only for less expensive worms, but also to ensure healthy, gut-loaded worms for your pets. Some people also like to eat them (not me-no way!) since they are a healthy protein source.

This picture shows a very full container of medium sized worms.  The bran is about to be refreshed. The clumping of worms is where there are pieces of carrot.

There are a variety of ways to raise meal worms that you may read. There is almost no “right” way to do it. You just need to find what works for you.

In this blog I will attempt to explain a method that has worked for me for nearly a year.

To raise meal worms it helps to know what they are. They are not true worms but they are beetle larvae. The worms you buy, if left alone with enough food, will grow and turn first into alien looking pupae, and then into small, black beetles. The beetles will then mate frequently (it seems all they do!) and lay eggs. Approximately 500 eggs can be laid by a female beetle in her life time. Eventually the eggs hatch into very, very tiny little larvae (worms) that will eventually grow to a size you can use in approximately 3 months.

The picture above shows meal worms at various stages of growth. The US and Euro penny show scale. They start much smaller than what is shown here. When they first hatch, you cannot even see them. I have to watch for the bran flakes moving a little on their own to know they are there. The pale, strange looking creatures in the lower, right corner are pupae. This is the stage right before they become beetles. If you look at yours, you will see little legs starting to form and the future wings are folded at the ventral (belly) side. It is neat if you catch one changing from a pupae to a beetle. Take the time to watch.

Basic supplies I use:

  • Wheat Bran
  • containers with lids (poke holes in lids for air to get in). I like to use 64 0z “throw away” containers.
  • baby carrots ( I prefer these. They do not smell as bad and less prone to mold. The entire carrot gets eaten as well)
  • sieve-small/medium mesh

Optional, but useful supplies

  • large plastic tweezers used to feed small animals or fish (these help to pick up individual worms or beetles from out of the bran)
  • clean newspaper
  • refrigerator with adjustable temperature
  • thermometer
  • clean paper towels

Quick Instructions:

Buy a batch of meal worms and let them sit out at room temperature until they become pupae. You may need to feed the worms on occasion by cutting slices of baby carrots and placing them into the container. This is fun to watch as they swarm the carrots and pull them under. The worms do not bite but they can crawl fairly fast.

When you get pupae, it often helps to remove them and put them into another container with a paper towel wadded inside. (I am not sure why the paper towel helps, but it made a difference for me.)  Let the pupae sit undisturbed until they become beetles. Be prepared for the abdomen (tail or back part) of the pupae to twist and spin around. This is creepy the first time you experience it but do not let it bother you. They cannot crawl anymore so they try to wiggle away.

Pour around 8oz of bran into one of the 64 oz containers (you can experiment with container sizes). Next place about 10-15 beetles into each container. Slice a few baby carrots and place onto the bran. The beetles will need this for water. Be sure to feed them the carrots once a week. Let them do their thing otherwise. They will mate, burrow, and lay eggs constantly. After about 10 days, prepare new containers and transfer the beetles to those. Note: you may put all of your beetles in one large batch but if something goes wrong, you will lose all of your worms. I found out the hard way to split them up into several smaller containers.

The containers that had beetles in them now are full of eggs in the bran. You may pour a few containers together at this point so you can free up containers to use. Let these sit and check on them periodically. You will eventually see the bran flakes moving slightly if you watch closely. This indicates that the eggs are hatching and you have very tiny worms moving around.

Let them continue to sit. When they are getting to the point that you can see them easily you can cut up a few baby carrots and place the slices on top of the bran. It is important that the worms get these on occasion for water. Do not forget your beetles too!

Continue to let them sit until they are the size you need. Unfortunately this may take up to 3 months for a worm to grow from an egg to a large adult. But once you have batches at various stages, you will always have some on hand. Small worms can be fed to small fish or birds. Larger animals prefer larger worms. Extra pupae can be fed out as well. Beetles are harder to feed to animals because they give off a small amount of acid as a defense mechanism. This is often not desirable to what you are feeding. The carapace or shell may also provide problems.

In the above picture I picked up a bit of carrot that had worms swarming over it. This only took a few minutes to happen. The carrot is in the center of the ball of worms. The flakes you see is wheat bran. The worms will not bite your hand.


There may come a time when you have plenty of worms at a size you like. You can slow down their growth when this happens. Store the worms in their container inside of a refrigerator. A dedicated wine cooler is great if you have one. Keep the temperature between 45-50 degree F. If they get too cold, they start to blacken and die. This smells bad as well. I store mine in the fridge door because the back of my fridge is too cold. A thermometer will help you determine this. The warmer the temperature, the faster they will grow.

Additional care of Worms

Poop Factories: As your worms are left sitting in their containers, they will be eating the bran and the occasional carrot. Eventually you will see what looks like sand build up. This is fecal material. Unless your containers are too damp, this material is dry. Pour the worms, bran, and poop together into a sieve and shake out the feces. The larger bran flakes and worms should be left in the sieve. If your worms are mostly tiny, wait until they are bigger or you will lose those as well. You may want to do small batches at a time so you can pick out any worms that get through. Add fresh bran on top and return them to their shelf.

Shed skins: You will also notice as the worms grow that you get this fluffy material on top of the bran. As the worms grow, they shed or molt their skin much like a snake. A freshly molted worm is white and soft. Eating one of these is similar to eating a soft-shelled crab. The carapace is there, it just has not hardened yet. As its new skin hardens, it will darken. When these skins pile up, just take the container outside and blow across the surface. The skins should blow away. Be careful of the angle you blow or you will get them in your face. Bleh.

Gut Loading

If you are using meal worms to feed to pets then you may want to feed the worms something that will benefit your pet. For reptiles, there are vitamins you can shake into the bran. Also, dust the meal worms with calcium and/or vitamins before feeding to the reptiles. I feed my worms flaked fish food on occasion. Just sprinkle on top of the bran.


Clean newspaper may also be used to stretch the bran or replace it. The worms will eat the paper though this is not as nutritional. I will shred some paper and mix with bran for the worms to improve air circulation through the bran and to allow the worms to crawl up onto the paper rather than each other should the bran get very low before I add more. Experiment and see.

Feeding to birds

Meal worms can be left in a container for birds to find. The container has to have slippery sides. Glass bowls or even empty, clean tuna cans work well. The worms cannot climb anything slippery. Wild birds go crazy for these. Captive birds, such as finches, may also like the smaller worms. Do not leave the worms in direct sunlight. They will quickly die. Note: Ants and other insects will like these as well. Try not to place the container on the ground. I place my container in the center of a hanging platform or open feeder.


  • Air circulation: You do not want moisture to build up inside the container. Damp bran is bad. You may get a green mold growing that will kill your worms. Once you get mold spores, it is difficult to get rid of the mold entirely. Do not mix that batch with other worms. If the mold is not too bad, just shake the container and keep an eye on the worms. Shake daily. If the mold is bad, throw out the worms and bran. If you save the container, soak in bleach water and let dry very well.

— One way to help prevent moisture build up and mold is to remove any uneaten carrots the next day. Another way is to shake the containers every few days to get air through the bran. Beetle containers have less problem as they are constantly digging through the bran. But do watch them as well. If you stack the containers, be sure air can get in through the holes and their is plenty of air movement in the room they are in.

  • Poison: Organic bran is recommended to prevent pesticides from being present and killing your stock. This is also why I settled with baby carrots. Lettuce and some apples had pesticides and who knows what on them. I have lost batches to this. So far I have been lucky with the carrots.
  • Infestation: Other insects may like the same conditions as the worms and move in. Others such as mites, will eat the worms themselves. This is why I like to keep lids on the containers (with holes). This helps keep pests and dust out. This is also why I store my worms inside, not outside. Removing wet food after 24 hours also helps. Just as a precaution, I also freeze my bran for at least 24 hours before using it. This will kill insect eggs that might be in it. Do not let the chance of infestation scare you from trying this. I only had one accident when I was first learning. I have been doing this a year and  have not had any problems since. If your worms do get infested, throw them out, bran, and all.

Good Luck!!

For more stuff to learn to do go to my main site https://virtuallyamy.wordpress.com/. Notice there is more than one page of blogs to go through….and more coming! Yay (again)!

Note (May 15, 2009): I have cut back production of my worms for various reasons. Now I use a few smaller containers (holds about a cup and a half of material) that I leave on top of my refrigerator. One container holds pupae I want to turn into beetles (otherwise I just feed the pupae to the birds-too many beetles mean too many worms).  Another container holds about 15 beetles that  I on occasion switch out to new bran to let the eggs hatch and grow. I keep about 3 containers of worms at different stages of growth. If I get too many of the old worms, they get fed out to the birds to keep them from pupating or dying and contaminating the bran, or to prevent my having just too many worms. There are always more coming behind them. I throw in sliced carrot once in awhile and sift out poop and refresh the bran. Raising this small amount is so much less work. You can mostly forget about them except to keep an eye on them once in awhile to feed them, watch for mold or mites, and change out the bran and beetles. Just remember to occationally let a few worms become beeteles to refresh the old ones.

I do not keep them all in one big container in case something happens to one batch. I got a mite infestation from something I brought in (really, really gross) and lost most of my worms. But since I had them split into several containers and spread out, I had one batch escape infestation to carry on my current batch.

Another precaution: If you get moths in your house (thanks to some bad wild bird seed), they will lay their eggs in that bran. The resulting moth worms are gross. Be sure you have lids with small air holes on your containers to keep them out.

If you are new to rasing meal worms you will find it simple. But do not be surpised if you get at least one nasty suprise while you are learning the ropes. Do not let that prevent you from doing this. It really saves you money if you need to use them frequently.


  1. I have been volunteering at a wildlife rehab center and they are having trouble getting meal worms. Perhaps this is the result of mites or mold. Anyway, I have been considering raising meal worms to give to them. Are you aware of any problems with supply of meal worms?

    Comment by Helen Norris — March 27, 2009 @ 4:46 pm | Reply

    • HI there! Yes, many of the major suppliers had their stock die out nearly all at once. This was nearly a year ago so it disturbs me that they are still having problems. I never found out the cause of the die out. Meal worms were like gold for awhile. There are still a few small distributors that sell them with little trouble though there may be some back order. You will need to do some searching online. I do not know the names anymore. I worked at a rehab place that raised their own and it really is the best way to go to save money in the long run. If you can get a donation of a few old refrigerators (or go to Goodwill) to dedicate to meal worms, you can keep a ready supply in large bins in there. Slows down the growth so you can keep up and helps protect from infestation of mites and mold if one is careful. You do not need to get it as complicated as what I posted either. Contact C.R.O.W. (they have a website) and ask them about their setup. It has been several years since I was there. Also, because of mites, I suggest not raising all of your worms in one container. If one gets infested, you may get lucky with the others. I had the misfortune of this recently and got lucky that one container in another room escaped. Let me know how it goes!

      Comment by virtuallyamy — March 28, 2009 @ 1:04 pm | Reply

  2. How can you keep mealworms as pets without feeding them to animals.Every website I see talks about raising them to feed them to pets or wild animals.

    Comment by allison — August 23, 2009 @ 4:44 pm | Reply

    • Just let them live out their cycle through beetles and not feed them to anything. Maybe get very large bins. Just keep in mind that they breed like crazy. They are prey animals so they are built to reproduce. This means they will eventually become so crowded that their living conditions will not be nice at all (and they will cannibalize) so you will either have meal worms over running your house as you get more containers or you will have to thin the herd. It may not look it in the pictures but I do try to keep them from being packed and living in poop and no water. They all come to the top for carrots so it looks like they are packed in. It may seem weird but they live in their food. This is normal. They will infest your grains in the cabinet the same way. You also have to watch infestation of mites, moths, and other critters in the grain you keep them in. Try to read up on the life cycle of wild grain beetles. There are science based sites out there to give you an idea what habitat they come from without going into raising them for food. Sorry, I no longer have the links.

      Comment by virtuallyamy — August 23, 2009 @ 5:18 pm | Reply

  3. My Mw’s are over run with Grain mites!!! is it possible to pick out the worms wash them and place them into a new container and beeding…I don’t want to loose all my mealies, I just bought $200 WORTH…

    Comment by Chris — November 23, 2009 @ 8:09 pm | Reply

    • Oh No!!! I know your pain! I honestly do not know if washing them would work. You would have to be careful of drowning the worms. The one time I had a major infestation, I lost them all. But I did not try to salvage. The mites are very hard to get rid of in an area and I found it best to get rid of them all. The wild birds in my area were fat and happy that week. I did not want mites infesting the entire house.
      I would move them to a different area or plan on putting future worms in a new area from where you have them now.
      Always freeze your bedding for a few days before use. It helps some to get rid of eggs and pests. Try washing the worms in small batches and putting them in several small containers. Maybe that way some will be ok and away from batches that are not. ? Do move the worms out for a bit to spray with bug spray all over the area. Return the worms after the spray settles so they do not get poisoned. I had to do this several times in an area and then put them up on a structure and spray the legs so they mites could not crawl up. Now I have them in a new area and am diligent about sticking with one brand of grain and leaving it in the freezer until I need it. So far, so good.
      I hate mites! I am still so paranoid about it.
      Are you using these to feed something? You can still probably use them feed out though it is gross. But again, I would get them out of the area you plan to keep them to avoid spreading mites around.
      Sorry I cannot be much more help! Companies that sell them have lost entire stocks to mites and I have not come across anyone with good advice on what to do. 😦
      Good luck.

      Comment by virtuallyamy — November 23, 2009 @ 10:56 pm | Reply

      • Thank you for your info,,I’m washing them as we speak..Holy Shi**en mealworms, but it has to be done..I’m moving them to a new location and I microwaved the new beding, hopefuly this will help..Yes I’m feeding Jones armadillo lizards, leopard geckos, buddgie bird and breeder rats and mice,Affacian fur rats also my turtle and fishs..once again thank-you..

        Comment by Chris — November 23, 2009 @ 11:48 pm | Reply

        • Good luck!
          Oh, be careful that the mites do not end up in the bird food. 😉
          Sounds like a long evening ahead for you. Bleh.

          Comment by virtuallyamy — November 24, 2009 @ 1:18 am | Reply

  4. Thanks to all for info..Just got done washing off all the cantainers and 25000 MW’s..Hope this do’s the trick..I will accecpt any other information on this Grain Mite matter,,I don’t mind them to much but the wife freaked{lol}..anybody know if the grain mite will harm my pet lizards..

    Comment by Chris — November 24, 2009 @ 6:29 am | Reply

    • Wow that was a lot to wash! I will keep an ear out for any other info and throw your way if I hear it. I guess visually inspect them before feeding out. I know mites can infest reptiles but I do not know if these would. Externally I mean. They can eat them though.
      I would not use any of this bedding for future worms you get. Only takes one mite with eggs to get it going again. I am sure you know already. 😉
      Hope you try keeping them again in the future. It does save money. Thanks for letting me know how it went!

      Comment by virtuallyamy — November 24, 2009 @ 11:18 am | Reply

  5. Hi,
    Just wanted to say thx for such an imformative blog. Ive been reading up a bit on meal worms this morning and out of everything ive read yours beats them all and without going on and on and on. Its sure to help.

    Comment by Aussie — April 1, 2011 @ 2:10 pm | Reply

    • Thanks! And of course there is plenty of room to adapt this method to your needs. This is just a suggestion for one way.

      Comment by virtuallyamy — April 1, 2011 @ 3:18 pm | Reply

  6. Hi,
    Is there any way of telling when the worms are about to turn into pupae??
    Or do I need to just keep watching them all??
    Also how long are they at the pupae stage??

    Comment by Aussie — April 6, 2011 @ 10:06 am | Reply

    • HI! Sorry so late in response. I did not get a notice that I had comments. 😦
      The worms start to move very slow and hang near the top. Very sluggish. Likely will not see them try to dig down fast when you pester them. This is how I know they are about to turn. I cannot remember how long it takes them. I have stopped raising them for awhile. But they are about to become beetles when they turn turn brown. They are very soft at first and will not harm the other pupae so you can leave them in there for a day or so. Be sure they have nooks to hide in. I started to put paper towels wadded up in with them to hide in and get away from the pupae. Once they are no longer soft, they will have the ability to chew on the pupae if they do not have a source of moisture.
      I will try to dig in my notes to find out the timing of it all but I wanted to comment now before too much time passed.

      Comment by virtuallyamy — June 12, 2011 @ 6:39 pm | Reply

  7. Excellent information Amy !!! Thank you!

    Comment by Pam Anderson — April 28, 2011 @ 7:39 am | Reply

RSS feed for comments on this post. TrackBack URI

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: