Feeding Your Reptiles: Mealworms

One of the main reasons why many people resist the idea of keeping reptiles as pets is the food requirements.  With a cat or dog you can just buy your food at the store or the vet’s office (or if you’re really fussy, cook a special diet for them out of foods that you would probably eat yourself).  With reptiles, though, there are insects and even mice and rats to consider as food items.  These “creepy-crawlies” can definitely be a turn-off to some people, and while there are some vegetarian reptiles out there (Mali Uromastyx are becoming very popular these days), they’re not as easy to find as the more common geckos and beardies — and choosing a pet based on diet really does limit your options.

When things really get difficult is when you start getting more than just one or two reptiles in the house.  With just one baby, it’s easy to hit the pet store once or twice a week to pick up a dozen crickets, and then feed the bugs to your lizard right away so that you don’t need to ever keep them around the house.  When you get more animals, though, those trips can become expensive — and with growing juveniles, gravid females, or other more ravenous critters in the house, you’d need to be going every single day.  And, of course, if you live in a small town or rural area you might not have a convenient pet store to make regular trips to.  So keeping your own colonies of bugs quickly becomes a good option if you’re getting serious about your herps.

Maintaining a good diet for your reptile pets is a bit more work than just operating a can opener — but if you get yourself set up right, it doesn’t have to be difficult.  I’m going to write a few posts about some basic insect setups that are easy to get going and even easier to maintain.

One really common choice (and probably the easiest thing in the world to keep going) is mealworms:  the larval form of the darkling beetle.  They’re high in protein, and for many lizards these are a great staple food — some of the longevity records for leopard geckos have been set by leos fed on a diet of primarily mealworms.  Many types of geckos (including leos and cresties), bearded dragons, chameleons, water dragons, and many other lizards will happily chow down on these little buggies.  Mealworms also make good food for some amphibians, birds, and tarantulas.  They’re even safe for human consumption (I’m told they’re delicious if fried, but have yet to try the experiment myself).  Look up your pet’s specific needs to see whether mealworms are an appropriate food or not — as always, do your research, people!

So Just What Are Mealworms?

As mentioned above, the mealworm is the larval form of the darkling beetle.  Like most beetles, there are several stages in the darkling beetle’s life cycle.  They begin as eggs, which hatch into teeny, tiny little mealworms after about 7-10 days.  The teeny, tiny little mealworms eat and eat until they outgrow their exoskeletons, which they then shed in order to become slightly bigger mealworms.  Whenever a mealworm moults, it will be a creamy white color for a day or two before the new exoskeleton hardens up and becomes the usual brown.  Some people like to select only these white, freshly-moulted mealworms as food for their lizardy-babies, as they’re less crunchy and more easily digested at this point — but it’s definitely not necessary to be so picky.  This process of moulting happens about 10-20 times, until the mealworm is about 2cm (just under an inch) long.  At this point the mealworm will enter its “pupal” stage, a form halfway between a worm and a beetle.  When in the pupal phase, the young darkling beetle is at its most vulnerable.  Like a caterpillar in its cocoon, it won’t move or eat for several days (up to a few weeks, depending on temperature and seasonal conditions).  If prodded it may twitch, but mostly it will just lie there.  After the inner transformation is complete, one final moult will occur, and a new darkling beetle will emerge, ready to eat and mate and create a new generation of lizard food.

Pictured below are several different phases of mealworm development:

Preparing a Mealworm Colony

The most difficult part of setting up your mealworm colony is simply getting your hands on several hundred mealworms to begin with.  Smaller pet stores may not be prepared to sell you 500 or 1000 mealworms on the spot — but they’ll likely be very happy to order them in for you.  Be sure to ask about discounts on bulk purchases like this.  There are also websites where insects can be purchased, such as canadianfeeders.ca — but do be sure to do some careful research before ordering anything online.  Some suppliers feed hormones to their mealworms to prevent them from ever pupating , as a way of ensuring that customers won’t just set up their own colonies.  It’s an underhanded trick, and I myself am definitely uncomfortable with the idea of feeding hormone-doctored bugs to my lizardy babies.

Once you have your starting population, all you need is a container (or preferably two or three) that are large enough for the mealworms to live comfortably.  If they’re living all jammed together there’s a greater likelihood of cannibalism, and waste will build up more quickly.  Your container needs to have a flat bottom and straight sides so that the mealworms can’t climb out, and some ventilation so that they don’t suffocate.  I use a simple plastic drawer unit (pictured below) with two drawers measuring about 16 x 24 x 6cm.  Plastic shoebox or tupperware containers (with air holes drilled in the sides or lid) also work well, but I like the easy access of the drawers.

In addition to a place to live, your mealworms need some food to eat.  Cereal grains (like uncooked oatmeal or bran flakes) are a great option, and they also give the mealworms something to burrow in.  I put a thin layer (less than a cm) of bran flakes on the bottom of each drawer.  There also needs to be a source of water provided, but mealworms can’t drink from a water dish — they’ll drown.  Slices of fruits or vegetables will do the trick, and feeding a variety of healthy vegetable matter to your mealworms has the added benefit of making them a more nutritious meal for your lizards.  If you’re a person like me who cooks with a lot of fresh produce, you can supply most of your mealworms’ needs by simply giving them the cut-off ends of carrots and other veggies that would normally just end up in the compost.

Maintaining Your Mealworms

Like pretty much all living things, mealworms produce waste.  And when they’re living in an enclosed space, that waste builds up over time.  Keep your mealworm colony clean and healthy by removing any dried-out bits of vegetables and fruits (or if something starts to go mouldy, take it out right away).  Also try to remove any dead mealworms or beetles.  And every month or two you’ll want to do a full clean-out of the container, to get rid of as much worm poop and other debris as possible (this is where having two separate drawers comes in handy).  How I handle the big cleaning operation is to move everything into a single drawer.  I then wash and dry the empty drawer.  Then I pick out any live beetles and mealworms, and move them to the fresh drawer.  Because the eggs can’t be seen, you can’t just throw out the rest:  sift it through a fine mesh strainer.  Keep whatever goes through the strainer in the second drawer (separate from the more grown-up beetles and worms), and throw out the bits of vegetable matter and cast-off exoskeletons that get caught up in the mesh.  Toss in some new grains and fresh veggie slices for the buggies to nom on, and you’re good to go again.

Occasionally it may be necessary to buy some new mealworms to “top up” your colony, if the population gets too low.  Keep an eye on things and if you see that your lizards are consuming mealworms faster than the colony is producing them, try to increase your population.  You can also start another colony if this seems to be happening far too often for your liking:  maintaining several colonies at once means that you can harvest from one and leave the other one alone to replenish itself for a time, and then switch over when the first colony starts to get a bit depleted.

Watch for some other insects that may decide to infest your mealworm colony, such as grain moths and grain mites.  Grain moths aren’t a huge concern (except that they’re a bit of a pest to have around the house, because they’ll get into your cereal and pasta and rice if it’s not kept in air-tight containers).  Grain mites are more of a problem, as they’ll multiply rapidly and make a mess of your colony.  If you notice that you’re getting non-mealworm bugs in your colony, give things a good cleaning out and consider putting a screen top on the containers to protect the colonies from further infestation.

Feeding the Lizards

Mealworms should be dusted with mineral and vitamin supplements (according to your lizard’s specific needs) before feeding.  In most cases, a calcium supplement is the most important.  Phosphorous and vitamin D3 are also commonly important ones.  Do your research and determine what is necessary for your specific animals, because mealworms alone are not an ideal diet.

You can also mix mealworms with other feeders, such as crickets, waxworms, butterworms, roaches, silkworms, superworms, hornworms, etc.  It’s not totally necessary (as long as you are supplementing properly), but a varied diet makes it easier to be sure that your reptiles are getting exactly what they need.

Potential Hazards and Concerns

While mealworms are generally a good feeder and don’t really pose many problems, there are a couple of concerns when using them as a major feeder for your reptiles.  One is the hard exoskeletons, which may cause a risk of impaction if your lizard is eating a lot of them.  It’s extremely rare that this will happen, but impaction (which can happen for a variety of reasons) is a leading cause of death in captive lizards.  For this reason you should always be aware of how often your lizard is eating and pooping, and watch for any abnormal behaviours.  If your lizard stops eating, stops pooping, or starts behaving strangely, you may have an impacted animal.  Check for dark or swollen places on the belly, and if you’re not sure, see a qualified reptile vet.

To avoid any risk of impaction, you can try to feed mostly freshly moulted mealworms (the white squishy ones).  As I said above, though, it’s a very small risk.

Another concern with mealworms is that with lizards who don’t chew their food before swallowing (sometimes an issue with bearded dragons, for example), the mealworms may bite on the way down, causing internal injuries.  There’s some debate as to how much of a threat this really is (some highly respected reptile specialists scoff at the idea), but if you are noticing that your reptile tends to swallow its mealworms whole and this is a concern to you, you can either a) switch to feeding larger prey items that will require chewing, or b) kill the mealworms before feeding them to your pet.  Be aware that some animals won’t take to eating pre-killed foods, so the first option is sometimes the only one.  Larger prey items may include crickets, silkworms, superworms, hornworms or roaches.


12 Responses to “Feeding Your Reptiles: Mealworms”

  1. I adhere to ones web site with regard to pretty quite and also inform your own content articles constantly to be able to involving unparalleled combination and also good pertaining to audience.

    • Thanks for the info. I have been obsessed with reptiles since I was a little girl catching lizards with my brothers I know run a small in home rescue after 2 years at a pet store and passing my reptile certification class. I just noticed my chameleons and monitors pretty much eat whole I give them a lot of variety but was wondering if swallowing the meal worms whole could result in internal damage Ive always done it but was curios. You helped a lot. Thank you and hope all your babies are healthy and happy.

  2. […] Feeding Your Reptiles: Mealworms « DomestiGothMar 10, 2010 … One of the main reasons why many people resist the idea of keeping reptiles as pets is the food requirements. With a cat or dog you can just … […]

  3. thank you for your guidance it will help me greatly. Can you chop the heads off the meal worms when feeding to leopard geckos so they are still dying when being eaten eliminating the risk of internal damage if the meal worms bite while being swallowed?

    • The prevailing opinion is that it’s really not a concern with leos and that the stories about injury are urban legend. Leos tend to bite & chew their food well, so by the time the mealworm gets swallowed it’s pretty well pulped up, and their stomach acid is strong: they’re pure insectivores, so their bodies are designed for eating crunchy desert insects. It’s only a concern if your animal tends to swallow prey whole (and even then, as I note in the article, it’s a minor concern that many experts don’t worry about at all anyway). Mealworms are an ideal food for leopard geckos and a very common diet for them; there simply aren’t substantiated reports of injury out there.

  4. Thank you it was really helpful to me….so how many mealworms do u think I should feed him

  5. June Bug Says:

    Thanks for the info on the hazards. I recently bought a veiled chameleon, and I have been feeding it crickets and mealworms. Today, one of my students told me mealworms can cause harm to our chameleon. Shocked and worried, I have been searching the web to see if that was true. Thanks again!

    • My daughter told me that she was told by a vet at the humane society where she works that the story of meal worms eating a lizard came from a case where the lizard died first and was only found after the meal worms had starting recycling.

      That said somebody on the internet saying “some guy told me…” isn’t exactly trustworthy info but I have been feeding my gecko mealworms for a while with no problem, though I have yet to try letting them hang around in his cage (I drop them in his bowl of calcium and watch to see he eats them).

      My crickets do live in the terrarium with him with no problems. I use towels as a substrate so they have places to hide, and the gecko likes the hunting experience.

  6. Thanks a bunch dude u really helped me care 4 my bearded dragon

  7. great read…first person to not completely bash meal worms with info from hobbyists!


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