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Making the Most of the Mealworm: some tips on enhancing the nutritional value of this pet trade staple

Today I’d like to take a look at a much-maligned food insect that can, if used properly, be an important addition to your pets’ diets.

Mealworms (larvae)
MealwormsA steady diet of mealworms (I refer here to the small mealworm, Tenebrio molitor, not the giant mealworm, Zophobus mario) is not recommended for any reptile or amphibian. These beetle larvae lack essential nutrients, the calcium: phosphorus ratio is not ideal and the exoskeleton is high in chitin. Mealworms also have quite strong jaws, and may injure debilitated or small reptiles and amphibians.

However, newly molted mealworms, which are white in color, are soft, have weak mouthparts and lower chitin levels. I have found them to be an excellent supplementary food for amphibians, tarantulas, scorpions and reptiles and fish.

Mealworms will shed most frequently when fed heavily and kept at 76-80 F. I house my colony in a mix of wheat bran, corn meal and powdered multi-grain baby food, with a bit of Tetramin Flake Fish Food added in, and provide banana skins for moisture.

Mealworm Pupa
Mealworm pupae are a fine food for turtles, newts, aquatic frogs and those lizards that accept non-living food items. They are low in chitin and likely have a different nutrient profile than either the larvae or adults.

Mealworm (Darkling) Beetles
Beetles, comprising the world’s largest animal family, figure prominently in the diets of most insectivorous reptiles and amphibians (based upon stomach content studies). I have long used darkling beetles (adult stage of the mealworm) as a food item, and prefer them over the larvae in most situations.

Beetles newly emerged from the pupae are softer than later-stage animals, and brown in color. To ensure a steady supply, I remove pupae as they form and place them into a bare container. In this way the beetles cannot burrow into the substrate, and are thus easier to harvest. Warm temperatures and a good diet (see above) will ensure a steady supply. Be sure to leave some beetles in the colony for breeding purposes.


You can learn more about the specifics of the mealworm’s life cycle at:

Image referenced from Wikipedia: http://en.wikipedia.org/wiki/Image:Mealworms_in_plastic_container_of_bran.jpg


  1. avatar

    Hello Frank,

    What animals have you found to take mealworm beetles? Have you any concerns about the presence of quinones? I understand they are quite potent defensive chemicals(superworm beetle adults seem even more powerful in this regard to me). I have fed them to tarantulas and they are taken eagerly(and beetle shells are often found in their garbage dumps near the burrow entrance in the wild) but after losing a 4.5 inch female Trinidad chevron(could well have been for other reasons) that had been fed a good number of these I have not been quite so enthusiastic with them.

    One cool tip I might mention is that mealworm pupa are great for feeding tarantulas near premolt, are being shy, or that you are otherwise not sure will eat. They can be placed somewhere and removed a few days later with no worry of them attacking the tarantula or hiding somewhere in the tank(their are horror stories of superworms/mealworms emerging from the substrate to attack a molting tarantula). They aren’t as readily taken as a cricket, of course, but are usually gone the next day. It seems tarantulas might be able to taste with their pedipalps/forelegs as they will pick up pre-killed prey items.

  2. avatar

    Hello Joseph, Frank Indiviglio here.

    Great bit of info concerning mealworm pupae, thanks very much. Tarantulas do indeed take dead prey, even if left for them to find and not tong-fed…I was surprised upon reading an article from a friend wherein he noted several species to take dead pink mice in the wild and captivity. Your note is the only other of the kind I have come across.

    I’ve fed mealworm beetles to a wide variety of herps, and have not had any reject the beetles based on taste, which might be expected if a defensive chemical were being employed. Beetles arising from super mealworms are quite large and with a thick carapace, but even these are taken by African plated lizards, frilled dragons, green tree monitors, marine toads (this last not worth mentioning, given their iron-clad stomachs, of course!) and some others. I don’t know of anything that has been done on the subject, research-wise, and so do not use the beetles exclusively for any animals.

    Thanks again for your observation, I’ll be sure to pass it along.

    Best regards, Frank Indiviglio.

  3. avatar

    Frank- ^-^
    Though I’ll probably consider replacing the meal worms with earthworms now, I still have a few left, and would like to use them if possible, though I’ll certainly cut them up into smaller pieces if you think this shouldn’t effect their digestion process etc.
    I was told mealworms will not change if you keep them together in a small plastic cup, have you found this to be true? If not do you have any tips for keeping them from changing? I know you can keep them cold and dormant, but then I guess they wouldn’t shed, and I want to make sure they shed for my little guys.
    also, I was told they’ll eat saw dust, and to leave them in the container with it, but the container has no holes, so I should probably add some right? and do they need the moisture or some form of water? also what are the best things to look for in fish food and such to feed them to ensure best nutrition value for the occasional one I give my frogs untill they run out? like specific vitamins, or calcium, etc.
    thanks a ton ^-^

    • avatar

      Hello Ayme, Frank Indiviglio here.

      Thanks for your note. Yes, cooling will prevent them from shedding…actually, you can let a few turn into beetles if you’d like, the beetles are a better food source than the larvae; otherwise, feed heavily as described in this article. The sawdust is just to provide a living space, they will not eat it. Moisture can be apple, orange or other fruit – banana skins work well as they dry out before becoming moldy. When mealworms are cut, they do not continue to move about like earthworms, but you might try using a feeding tongs.

      Good luck and please keep me posted.

      Best regards, Frank Indiviglio.

  4. avatar

    I’ll have a look, it’s appreciated ^-^
    they both respond well to spoon feeding as I’ve had a couple crickets drown from getting knocked around in the water before they manage to catch them, and they seem to have learned it’s still good; while I try not to have to, they will respond to it so I’m sure they’ll eat them, thankyou. ^-^

    • avatar

      Hello, Frank Indiviglio here.

      Thanks for your note; it’s good that they will feed in that way – very useful if they ever need medication, or if you want to be sure each is getting enough food. Sounds like you are doing very well,

      Good luck and please keep me posted.

      Best regards, Frank Indiviglio.

  5. avatar

    I completely agree on your statement of not using mealworms as a complete food staple, and what you have mentioned in previous articles about a varied diet. I experienced the effects of this last summer when I took care of a friend’s adult bearded dragon. I gathered that he had fed the lizard almost exclusively mealworms since it was young (when I asked him about plant material, he had no idea it was even a possible option). It was apparent that the animal was lacking in some nutrients/vitamins, and it noticeably affected his behavior and appearance. The muscles in his hind legs appeared to be overwhelmingly underdeveloped, and to move he dragged himself around only with his front legs. It was unusual for him to move more than one or two feet a day, usually to and from his basking spot (kept in a 3 foot square enclosure, probably 18 inches high). Aside from that, the only other movement he seemed capable of was to lift his head up about an inch or so.

    While I had him, I was able to add some variety to his diet, including crickets, dubia roaches, and whatever I could catch outside, as well as various vegetables and mixed greens. The crickets I set loose after I dusted them with supplements, and he seemed to genuinely enjoy chasing after them as best he could with his disabilities. It was kind of pathetic to watch, but he turned out to be a surprisingly efficient hunter, timing it just right so he could catch the insects with his 2-inch striking range. And by the end of the summer, he actually seemed to be in better health than when I got him. He certainly seemed happier, at least. I had a talk with my friend, and he’s done his best to improve the animal’s diet, which upon the last report I heard, is doing well.

    • avatar

      Hello Jeremy, Frank Indiviglio here.

      Thanks for the most interesting post. It’s especially useful for readers to see how steps such as those you’ve taken can make a real difference in an animal’s health.

      Some of the problem’s you describe are typically seen in Calcium-deficient lizards. Since the lizard responded well to diet changes, it would likely be worthwhile to follow up with Calcium Gluconate injections or similar treatments, which may result in further recovery. An experienced vet can also test for Vitamin A and other common deficiencies. Please let me know if your friend needs help in locating a vet, or if there is anything else I can do.

      Good luck and please keep me posted…it’s very useful to be able to follow an individual’s progress and treatment.

      Best regards, Frank Indiviglio.

  6. avatar

    Hi I have 2 american toads, and am trying to get them fattened up before releasing them… one seems to be less aggressive at catching prey, and gives up when the item isn’t instantly (successfully) caught. The other is a voracious eater / hunter. This is true even if fed alone in a tub or bucket. So she just gives up and hibernates instead.

    2) sometimes they turn very dark color, and not sure if that’s a sign of illness.

    3) i m having a hard time deciding where to release them. ( we had a garden toad outside for 3 years – and occasionally fed her mealworms and were delighted at her appearance each spring – but then last year I found her “weed–wacked”accidently by the yard worker – it was so sad – she had cuts all over her, including one eye, and she was dead by the next morning…

    That’s why we caught and took in these two toads – so they wouldn’t have the same horrible fate…(run over by a lawnmower or killed by a weedwacker). – they belong in the wild – they have nothing to do and can’t hop around + feel the sun and breeze –

    So I would feel better if I could find a safe, suitable place to release them.

    Also, we see “creepy” tiny things in the cage + get tiny annoying gnats from the cage, and the mealworm cage got infested with some type of almost microscopic yellow/gold mites or something that seem like something straight out of a horror movie –

    If too wet of food is placed in the mealworn cage, then soon a live flowing “mass” of gold “fuzz” starts growing OUT and OVER the edge of the container – onto the floor, wall onto everything near it – + I can’t find any way to kill them (online) even lived in the freezer – big mistake – thought that would kill them… worried out of space so will end here. – parks ? (No soft dirt to burrow, and probably poison – botanical garden ? Lots of tilled dirt, but bug and weed poison ?

  7. avatar

    Want 2 american toads ?? Lol

    I want them safe + well cared for,
    Or released and happy + safe in the wild.
    They have no quality of life in this 20 gallon tank…
    Seems more like a prison or cage than a home,
    Despite setting it up nicley…

    There’s just nothing new to do and no large areas to run around… when I set them outside they are across the entire yard in minutes, so you can tell they enjoy moving, hopping + exploring… wish I could find a safe place to release them, where they’d have soft dirt to burrow in.

    • avatar

      Hi Debbie,

      Very nice of you to be so concerned. Mealworms should only be used sparingly, when freshly molted. Toads need a highly varied diet along with vitamin/mineral supplements if they are to thrive (studies show that an adult may consume 20,000 insects per season, including dozens to hundreds of species). You can read more about toad/frog nutrition and care below (note: both articles have 2 parts, link to part Iin text)..I’d be happy to help you devise a diet, but if you’re leaning toward release that would be fine at this time of year. No need to fatten first, etc…in a suitable habitat, they have all the instincts needed, and plenty of time before winter.

      They do well in garden type habitats, sometimes better than wild , but there’s always a downside…same with a natural habitat – predators, disease, weather events etc – really no way to predict, no point in over thinking. For each adult that survives, thousands do not. If they are showing up in your garden, then there will likely be a more suitable habitat within a mile or so. or you can release in general region….overgrown fields, forest edge, etc…no need to worry about soil type….they also shelter below fallen logs, rocks, debris, and in mole, and rodent tunnels. Pesticide occurrence is very difficult to trace…golf courses, etc, will be overloaded, but any semi=natural habitat will be affected, due to wind, movements of animals that have been sprayed, etc…no way to avoid; amphibs can cope to some degree, many variables. Pl let me know if you need more info, Best, frank

About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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