Beetle Substrate Guide

A how to guide on making flake soil for rhinoceros and stag beetles!

Unfermented Substrate

This type of substrate is simply just raw sawdust. This substrate is useful for keeping adults and making other substrates, but it is nutritionally inadequate for any beetle larvae. The tough biopolymer prevents the beetle larvae from consuming the nutritious biopolymer cellulose. Stag beetles possess the enzymes required to digest lignin, but even then an unfermented substrate is unsuitable

Types of Hardwood

Too long? Basically, I personally think white oak is the best, but red oak, beech, and most hardwood are good too!

Hardwood is a must have for flake soil. The majority of rhino and stag beetles have larvae within hardwood. However, many species like Xylotrupes gideon and other rhinos with the common name coconut beetle are commonly found within rotting coconut trees instead. Interestingly enough, genetically speaking, palm trees, the family Arecaceae which are all monocots, are not very related to oak trees and other hardwood, which are all dicots. Despite the prevalence of rhino beetles naturally ovipositing into palm trees, I would not recommend them within a general formulation for rhino and stag beetles for optimal growth. In contrast, I really do not recommend you to use softwood trees for the production of flake soil, these are gymnosperms like pine trees. This is due to many reasons, it is very unsuitable for both insects and the fungus they highly depend on in the wild. For example, oil from pine trees have many antifungal, antimicrobial, and insecticide properties. Due to these reasons, it is also not recommended to grow mushrooms or kinshi with softwoods. You really would not want your beetles to be eating this stuff. However, theoretically it is possible for these compounds to eventually degrade, which I am guessing will mean it will have a much longer fermentation period, because it is also possible to ferment softwoods to the point where certain hardwood loving mushrooms like Pleurotus can grow on them. Even then, this is highly unadvised – do not blame me for any deaths!

Within Japan the two types of hardwood most often used is a type of white oak and beech. In America, beech is not often used for flake soil production due to its unavailability in the wood pellet form people like to use. However, some manufacturers in Japan say that the advantage of beech is it degrades and also gets used by mycellium much faster than oak, perhaps owing to the fact that it is slightly less dense than oak. In America, red oak is more prevalent and cheaper, however I do not think it is as desirable for our beetle production as white oak or beech. Why do I say this? I think in theory the only difference between the different hardwoods is the organic compounds it contains, that is often used for flavoring, tanning, or insecticides. An organic compound contained within all hardwood trees that is undesirable is tannins, these are naturally insecticides and fungicides. Due to this, red oak and other dark colored woods like mahogany are less desirable for flake soil production. In theory, it may slightly benefit the beetle if you were to strain out the tannins from the hardwoods, even white oak, after soaking them in water, but this is not something I have heard of anyone doing before. Mahogany is also an example of a tree I would highly advise against using if possible, this is because a lot of them are known for their insecticidal properties, like the neem tree. If you don’t know, neem oil is often used in organic gardening as an insecticidal spray. It is also a very dark wood, high in tannins. Mesquite also has a high tannin content and many other alkaloids, hence its dark coloration. I wouldn’t see a reason to use this if you have access to oak. Generally speaking, I would personally prefer lighter colored hardwoods to darker colored hardwoods for maximizing growth and success with rearing larvae in flake soil. As I will mention though, most beetles are not too picky with the type of hardwood they can be reared in, with oak and beech not being the only host wood for Lucanus cervus or Lucanus elaphus or Dynastes tityus.

Lignin is the undesirable part of the wood, whereas cellulose is the most desirable part. This is mentioned in the first section. Due to this, I highly recommend sawdust that does not contain bark for making flake soil. I also recommend removing bits of bark from rotted wood that you find before you use. Why? This is because the bark has a very high lignin content, and also negligible cellulose content. It is not very useful for the beetle larvae.

I Really Can’t get Oak or Beech, can I use ____?

This is a question often asked. People who ask this question should read the above paragraph. However, it has been reported by authors such as Manee (1915) that Dynastes tityus larvae has been found within “wild cherry, black locust, oak, pine, willow, and other trees.” In addition, various stag beetle species larvae, like Lucanus cervus, have been known to be found in ash, apple, and cherry trees as well. You can easily Google this yourself to find this. In addition, the cosmopolitan presence of stag and rhino beetles highly suggest that they are by no means limited to only growing within oak and beech wood. What is my advice pertaining to this? If you ferment your substrate enough, beetles can survive in most hardwood and apparently some pine trees. Is it ideal? No. Do I recommend it? Not really, but I’d say most hardwood would be okay if fermented enough. However, if you are daring enough to use a softwood like pine or a very dark hardwood, I would highly recommend you to ferment the substrate for additional time because it is likely to take longer for it to be suitable. I am not responsible for any deaths or sickness caused by this though… I have no experience with using any wood besides oak, but I imagine a light colored wood like apple wood could potentially be used just like oak. However, I cannot guarantee anything.

Primary Fermented Flake Soil

This type of substrate is sawdust that was at least fermented once. It is much darker than unfermented substrate, but it isn’t nearly as black as a double fermented flake soil. This stage of flake soil is the best for most stag beetles, such as the genus Lucanus, Dorcus, and Phalacrognathus. However, it is not ideal for rhino beetles such as Dynastes and also certain stag beetles, such as Cyclommatus. This is the ideal flake soil stage for any american stag beetle.

Secondary Fermented Flake Soil

This type of substrate is sawdust that has been fermented twice. It is very dark and black, very close to garden soil. This is the ideal fermentation level for rhino beetles, such as those in the genus Dynastes. This is also the ideal fermentation level for Cyclommatus. Any more fermentation, such as a third fermentation, may benefit beetles, but it is risky and may lead to a high mortality rate. I personally think it is more optimal for someone to double ferment flake soil instead of fermenting their soil for longer. This is because it is more nutritious and faster this way. A lot of English tutorials state a 2-3 month fermentation for stag beetles and a 4-6 month fermentation for rhino beetles using the exact same recipe, but it is much easier to simply do a batch with multiple fermentation. In addition, each fermentation can actually be much shorter than 2-3 months in ideal conditions. I have personally made flake soil suitable for stag beetles in less than a month during the peak of summer.

But why should I double ferment or ferment longer?

Fermenting/composting longer without adding an additional nitrogen source or amendment does mainly one thing, it allows the lignin to breakdown farther to allow the beetle grub to access easier to utilize organic compounds like cellulose. Breaking down lignin is an energetically costly process, hence why we want the bacteria and fungi within our compost to do it ahead of time before our beetles need to.

Double fermenting, or adding more amendment after your first fermentation peters out does mainly two things. It breaks down complex organic compounds like lignin, as mentioned for fermenting longer. It also adds additional nitrogen to the soil for the beetle to have access to. Normally wood only has less than 1% nitrogen, it is mostly carbon base. Thus, the growth of stag and rhino beetles are mainly nitrogen limited. Adding amendments to the flake soil provides additional nitrogen, which speeds up decomposition and fermentation, but also leads to an end product with more nitrogen. Theoretically, the more nitrogen rich your soil is, the easier your beetle will have to grow in size. In practice, too much amendments added in order to increase the nitrogen content of the soil can cause high mortality rates in your beetles – you do not want to overdo this.

White Rotten Wood

This type of substrate is made from hardwood that has been attacked by white rot. This includes wood that has been used for mushroom cultivation such as shiitake logs. White rotten logs are useful for breeding stag beetles of the genus Dorcus and Phalacrognathus. White rotten wood should be shredded finely for stag beetle larvae, you can see this behavior in some stag beetles grinding up the wood before laying their eggs. This wood is not ideal for rhino beetles. This is actually the most ideal type of wood substrate for size and growth, save for kinshi, for the vast majority of stag beetles, such as the ones in the genus Dorcus, Lucanus, and Phalacrognathus.


Kinshi is the most ideal substrate for the vast majority of stag beetles, such as those in the genus Dorcus, Lucanus, and Phalacrognathus. This substrate is what is used to achieve record breaking sizes. However, it is largely unobtainable in North America and Europe. Kinshi is essentially myceliated hardwood sawdust from mushrooms such as the turkey tail or oyster mushrooms. Kinshi is actually essential for breeding certain exotic species such as Alloptopus rosenbergi. Kinshi bottles can also be used like white rot logs when breeding stag beetles. Although it is nearly impossible to buy in North America and Europe, there are methods online detailing how to make kinshi simply at home with a pressure cooker, sawdust, mushroom spawn, and some bottles.

Mushrooms used for Kinshi:

  • Pleurotus ostreatus – Pearl Oyster Mushroom Winter oyster mushroom, fast growth. Good for Dorcus and Phalacrognathus
  • Pleurotus pulmonarius – Lung/Pheonix Oyster Mushroom Summer Oyster Mushroom Prefered for more tropical species due to its tolerance to heat and faster growth
  • Trametes versicolor – Turkey Tail This is the ideal species for beetles in the genus Lucanus. Some people state that Lucanus elaphus would not benefit from kinshi, but it actually greatly benefits from kinshi made from turkey tail. However, this is not often done because of kinshi’s inaccessibility in North America
  • Hericium erinaceus – Lion’s mane
  • Lentinula edodes – Shiitake Actually not often used for kinshi, but the production of it leads to a common byproduct of white rot wood

Used Stag Beetle Substrate

After your stag beetle has utilized the substrate you have fed it, if you were feeding it substrate of primary fermentation level it is possible to use as a substrate for rhinoceros beetles. Although this is not ideal, it is completely suitable for Dynastes tityus and Dynastes grantii. Both species are very hard and easy to keep, and can easily deal with subpar substrate.

Basic Flake Soil Recipe

You can scale this recipe up or down as you desire. For ease, I advise you to use a breathable bag or compost roller.


  • 80 cups of Traeger oak pellets
    • This can be found in any hardware store, but can easily be bought online as well.
  • ~80 cups of warm or boiling water
    • -This is the most variable part of the recipe, add enough water until it is moist, but not wet enough to squeeze water out with your hands
  • 4 cups (500 grams) of flour or wheat bran
    • change proportion as desired, it is recommended to go with only wheat bran if you have no inoculant.
  • 1 tsp of yeast
    • You should activate this with a half a cup of lukewarm water and tbps sugar, waiting for it to at least bubble. You can substitute this with a can of beer!
  • 1 cup inoculant
    • More is better. Mix this with lukewarm water to ensure proper coverage over your unfermented sawdust blend. Inoculant can be rhino/stag/flower beetle frass (beetle poop) or be previously fermented/decayed wood/flake soil.


1. Prepare the sugar-yeast slurry with 1 tsp yeast, half a cup of lukewarm water, and 1 tablespoon of sugar

2. Mix the oak pellets with the warm water. Doing so in smaller batches and putting it into a bigger container is helpful

3. Wait until the oak pellets are no longer hot, it can be lukewarm

4. Mix in 500 grams of flour/bran into the oak flakes, make sure to evenly distribute it. Using a sieve and making sure the flour isn’t in clumps helps out a lot. Make sure your substrate does not clump and break up any visible clumps down.

5. Mix in additional water until the substrate is ideally moist, but not wet enough to squeeze water water with your hands. Err on the side of dryness.

6. Make sure the substrate is cooled down. Mix in your yeast-sugar-water mix thoroughly throughout your substrate

7. Mix your inocculant, beetle frass or used substrate or previously made substrate, with some water. Mix this slurry with the substrate

8. Ideally everyday, mix your substrate to aerate the interior of the substrate. Do this until the substrate stops heating up and also has a nice earthy smell. Make sure to keep the substrate hydrated throughout the process, a dry substrate does not ferment properly. If you do not mix your substrate often enough, it is more likely to be covered in dangerous (for your own health) mold and/or turn rancid.


1. It takes usually at least 3 weeks to properly ferment substrate once.

2. This process is ideally done in the summer because the cold will halt the process. The warmer the better (up to a certain point)

3. If it has an off smell, such as vinegar, beer or rotten food, towards the end of the process, your substrate has failed and needs to be dried and restarted.

4. Make sure that your substrate is sealed, but still has access to air, or else it will attract pests such as gnats or mites.

5. Substrate should be fermented at least twice for rhinoceros beetles, if you are trying to breed the largest rhinoceros beetles.

6. Additives, such as wheat flour, simply provide a nitrogen source to speed up the fermentation process, we are essentially forcing a “hot” fermentation. As long as the sawdust is hydrated enough, it will continue in a slower, “cold” fermentation.


To stably store fermented flake soil long term, you must dry out the substrate first. This should greatly slow down fermentation.

1. You must note that, even without the addition of a nitrogen source, the bacteria/fungi in the soil will continue to breakdown the lignin and cellulose in the flake soil

2. You may not need to do this if you happen to keep both rhino beetles and stag beetles and thus can utilize any level of fermentation. However, you run the risk of mold and thereby fungus gnats. This is because the substrate can still be utilized by bacteria/fungi as mentioned before.

Feel free to contact me at with any questions!

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