Home | Field studies and notes | Flour Beetles (Confused or Rice Flour beetles, Tribolium confusum and Red Flour Beetles, T. castaneum) – a valuable food for small amphibians and reptiles

Flour Beetles (Confused or Rice Flour beetles, Tribolium confusum and Red Flour Beetles, T. castaneum) – a valuable food for small amphibians and reptiles

Flour beetles of various types are serious pests in grain product storage facilities, and those discussed here are worldwide in distribution.  However, the traits that make them successful invaders also render them easy to culture in captivity.

The larvae, or grubs, of the beetles offer an easy way to add nutritional variety to the diets of tiny reptiles and amphibians, most of which must subsist on only a few food items in captivity.  The adult beetles release an irritating gas when disturbed, but are none-the-less consumed by some reptiles and amphibians.

Obtaining Flour Beetles
I was first introduced to flour beetles some 20 years ago by Bob Holland, an amphibian expert who was setting longevity records with poison frogs long before most zoos kept any at all.  In those days, we collected our founding stock by searching through old containers of dry dog food and cereal.  Today, cultures of confused and red flour beetles are available from private breeders and biological supply houses.

Culturing Flour Beetles
Although most beetle breeders advise keeping the animals in a mix of flour and yeast, Bob’s method of rearing them in dog biscuits has worked very well for me.  The problem with a flour mix is that the medium must be sifted through a fine net each time larvae are needed, which leaves one with unwanted beetles, pupae and shed skins.

Dog biscuits provide all the food, moisture and shelter needed by the beetles (be sure to crack open the biscuits to give the beetles easy access to the interior).  When larvae are needed, I simply tap a biscuit over a Petri dish.  The larvae can also be concentrated by tapping several biscuits over a separate container, into which only 1 biscuit has been placed.  All the grubs will eventually gravitate to the 1 biscuit, allowing you to collect many in a short time.

Using Flour Beetles
The adult beetles live for approximately 1 year, with the period from egg to adult being 4-6 weeks, depending upon temperature.  The larvae are 3/16th of an inch long when fully grown – an ideal size for poison frogs, harlequin frogs and newly morphed froglets of small species such as spring peepers.  I have also fed them to red-backed and red salamanders, the larvae of various newts and to small granite night lizards.

An article concerning the natural history and pest status of flour beetles is posted at:


  1. avatar

    Not sure through your description how the dog biscuit method eliminates the problem of adult beetles mixed in with the larvae….explanation would be great! I’ve tried just about everything(with the flour method) and eventually resorted to blowing off the shed skins…and then picking out the larvae to seperate from the beetles.

  2. avatar

    Hi Joseph,

    Frank Indiviglio here.

    Thanks for your question. As you suspect, my technique offers only a partial solution to dealing with these useful but frustrating little beasts.

    I prefer the dog biscuit method because it involves less substrate – the grubs and adults live within the biscuits. When you crack a biscuit, some of it does crumble and fall out with the insects, but far less is generated than with the flour method, and the biscuit pieces are quite large and easy to remove. If done over a bare feeding dish, you can pick out the crumbs and beetles if so desired, but I usually leave as is….some dart frogs will take the beetles as well as grubs.

    Thanks as always for your interest…sorry I wasn’t clearer in differentiating the 2 culture methods.

    Best, Frank Indiviglio.

  3. avatar

    hello, my auntie works at the university and rescued some from a students room before the exterminator came. She would like to know whether they like musicc and what is the best container to keep them in

    • avatar

      Hello Zoe, Frank Indiviglio here. Thanks for your interest in our blog.

      Well, this is the first “flour beetle rescue” I have heard of…congratulations!

      Plastic terrariums make ideal containers – choose one with more floor space than height, such as the Flat Faunarium. The beetles rarely fly when given enough food, but, just in case, check their size against the ventilation slots in the terrarium’s cover. If they can squeeze through, you can cover the slots with fine insect screening. This is available at any hardware store – ask for the soft type, which can be cut with a scissors. You can attach it to the terrarium with Aquarium Silicone.

      While working at the Bronx Zoo, I used classical music to block out noises from disturbing a colony of naked mole rats, which were new in zoo collections and very sensitive to sudden sounds. However, not much is known about insect hearing abilities…but since flour beetles can be found in very noisy grain processing warehouses, I believe that they are fine with or without music.

      Good luck, enjoy and please let me know if you need any further information,

      Best regards, Frank Indiviglio.

  4. avatar

    I must be stupid. I cannot find any larvae in my colony of confused beetles! There are lots of small, squarish wafer-looking substances. What are these? I’ve never seen these mentioned … I had the beetles in a small container for 2 months. I sifted the contents but saw only shed skins, the aforementioned wafer-looking things, and beetles. Then I moved them to a clear shoe box with more flour-food mix. That was 2 weeks ago. What do I need to do now? Thanks for any input!

    • avatar

      Hello, Frank Indiviglio here.

      Thanks for your interest in our blog.

      You’re probably just confused (Sorry!). Seriously, if you are finding shed skins then larvae were there at some point, as the adult beetles do not shed. Sometimes hatching and shedding occur more or less in sync, so if you don’t check for awhile you may miss all the grubs.

      The squarish objects may be the pupae – this is the immobile stage, as in butterflies and moths, during which the larvae go through metamorphosis.

      Here is a link to photos of the pupae and larvae, as well as useful natural history information:


      Good luck and please let me know what happens.

      Best regards, Frank Indiviglio.

  5. avatar

    😀 yes, confused is the more apt!
    Thanks, Frank. The link you sent cleared up the matter. Now I know what to look for. The squarish, wafer-like flakes, amazingly, must be the eggs. So I’m a bit early on the cycle for pupa or larvae. I’ll keep checking every couple of days.
    I really appreciate the help.

    • avatar

      Hello, Frank Indiviglio here.

      Thanks for the feedback; glad you cleared it up.

      I didn’t think to mention eggs, got sidetracked by the shed skins. Once the colony takes off, you can get some very high production; an old friend relied heavily upon the larvae as poison frog food, and set a few longevity/breeding records back before even zoos were keeping many species. Check your temperatures as well if you want to speed up their life cycle.

      Good luck and please keep me posted.

      Best regards, Frank Indiviglio.

  6. avatar

    Suppose if I fed my aquarium fishes food (dried bloodworms)infested with red/confused flour beetle, will it cause any harm to the fishes. The fished do not touch the beetle. But likely to eat food with larve and eggs of the beetle.

    • avatar

      Hello, Frank Indiviglio here.

      Thanks for your interest in our blog.

      Interesting question….the eggs and larvae are great foods for most tropical fishes, so go right ahead. I used to “inoculate” trout chow with beetles, for that very reason! If you don’t mind doing so, grind the food a bit with a small stone or something similar before using, and the fishes will be able to consume the beetles as well.

      The only concern might be that, if the beetles are present, this may mean that the package was opened at the store, or is very old. However, freeze-dried foods have an extremely long shelf life, so this is probably of little consequence.

      Good luck, enjoy and please keep me posted.

      Best regards, Frank Indiviglio.

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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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