How to make Flake Soil for Beetle Breeding
Written by: Richard’s Inverts
Japanese Rhino Beetle larvae (Trypoxylus dichotomus) on Flake Soil
General Information
This in-depth Flake Soil recipe of mine was first published online in 2020 with the aim of making beetle breeding more accessible to beginner hobbyists. Many new recipes derived from my original recipe/ guide here have appeared throughout the web since then, which I am very happy to see as it is evidence that more people are getting involved in this hobby! As this is the original recipe which most other recipes online have been based on, please do not hesitate to contact me if you have any queries regarding any of the information here, or the safety of potential new additives that many of these new guides have been including. :)
What is Flake Soil?:
FS (flake soil) is a type of highly regarded substrate that is suitable for the rearing of beetle larvae. It can be made at home quite easily by adding various additives to sawdust and fermenting it for a period of time until it turns into a uniform, soil-like substrate. Flake Soil is the go-to substrate for advanced breeders as it performs exceptionally better for larval growth and overall adult size than the conventional leaf / wood substrates collected from nature.
Normally when using substrate collected from nature, different types of materials have to be collected depending on the type of beetle: e.g. leaf mulch for Cetoniinae (flower beetles), well-decayed wood for Dynastinae (rhino beetles), and mid-decayed wood for Lucanidae (stag beetles) which I have outlined HERE. With Flake Soil however, it is a one fix solution to this painstaking problem as it can be used to feed the larvae of all three types of beetles listed above, and the nutrient levels can be controlled for the growth of large, healthy larvae as it is prepared from scratch at home.
Raw sawdust that has not been fermented yet cannot be used for beetle larvae due a tough, complex molecule in wood called lignin that provides rigidity and structure in trees. As beetle larvae are unable to digest the lignin, the main source of their nutrients called cellulose (a polysaccharide) essentially remains ‘locked in’ inside the wood by the tough lignin. The fermentation process which converts the sawdust into Flake Soil destroys this tough lignin, providing access to the nutritious cellulose that beetle larvae can process.
When sawdust is fermented, the colour and smell can be checked to help get an idea of the fermentation level of the Flake Soil. The colour will progress from a light yellowish colour of wood at the start, to a dark, chocolate colour at the end. The progression of the smell will be from a sweet wine smell, to a yoghurt-like smell, to an earthy soil smell at the end.
Additives in Flake Soil?:
Flour is the core protein additive used when making Flake. For advanced breeders, some optional additives can be used such as wheat bran, soy flour, buckwheat flour, chitosan, and royal jelly to name a few, depending on the desired result. The core protein additive I recommend when starting out at first is just plain white flour. Other types of additives mentioned above such as soy flour are richer in nutrients and protein, which can increase the nutritional content of the flake soil, but it also makes it much easier for the fermentation process to fail and rot to take place due to the additional nutrients. An easy way to think about it is the following: the higher the nutritional value, the more likely it is for the flake soil to rot instead of fermenting.
It is important to note that the raw additive itself is not eaten by the larvae. The purpose of the additives when making flake soil Is to kick start and aid in the fermentation of the wood, while incorporating the nutrients into the Flake Soil when processed by bacteria.
Additives must be added in moderation, even if it leads to successful fermentation and good looking Flake Soil is made. From my experience, I recommend that the percentage of the weight of additive should not exceed 8% of the total volume of Flake Soil. This is because as an unnecessarily large volume of additives in the flake soil will shock the larvae, and will severely increase the mortality rate. Larvae that do not die straight away from the bad flake soil will eventually suffer from health problems down the line, such as a compromised immune system or malformations when pupating / developing into an adult.
Boxes of fully fermented Flake Soil
My Tried and Tested Recipe for Flake Soil Substrate:
The following ingredients are the measurements requiered to make 10 L of flake soil.
Ingredients:
10L Sawdust Mixture (80% sawdust 20% frass / old flake soil)
200g Flour
50g Sugar
10g Brewer’s Yeast
Optional special additives for advanced breeders:
100g Trehalose
20g Cellulose Powder
10g Chitosan Powder
10g Glutamic Acid
Steps:
Measure/weigh each component, then mix all the dry ingredients together in a tub (sawdust + flour + sugar).
Add 10g yeast and 5g sugar to a measuring jug with 500 ml of lukewarm water. Stir well to dissolve the yeast and sugar, then leave the mixture to sit for 30 minutes to allow the yeast to ‘awaken’.
Pour the yeast mixture into the sawdust in the tub and mix well.
Add water until the substrate is moist but not till the point where it is sopping wet. As a guide, add water up till the point where you can squeeze a ball of the substrate and the ball holds its shape. If water starts dripping out when squeezed, too much water has been added.
Flatten out the sawdust mixture and lightly compress to remove any air pockets.
Place the lid on the tub and store the container in a place warmer than 23C where stable fermentation can occur.
Stir the substrate well after 1 week has passed. By this time, the fermentation will have already started which is evident from the alcohol-like odour and the emitted heat due to bacterial activity.
Stir the substrate well every 2-3 days until the fermentation has completed which will be evident from the smell of earthy soil once finished. Your flake soil is now complete. This usually takes 1 month to complete under my conditions but can take less time or longer if kept warmer or cooler, respectively.
Richard’s Flake Soil Making Tips & Precautions:
It is easier to make flake soil in the summer than in the winter as the bacteria that break down the sawdust and process the additives work better at higher temperatures.
The flake soil will rot if there is too much moisture. The main cause of fermentation failure and rot is oxygen deficiency and excessive organic additives.
If the Flake Soil smells like vinegar, ammonia, or faeces, it is a sign that there was fermentation failure and rot took place. If this happens, the substrate can be fully dried out to remove the rot causing bacteria and Flake Soil production can be reattempted.
The higher the nutrient content of the chosen additive, the greater the chance the substrate will rot instead of fermenting into Flake Soil. I therefore recommend plain white flour as the sole additive for beginners.
The greater the volume of the chosen additive, the higher the nutritional content of the Flake Soil, which will result in large adults. On the other hand, an absurdly high volume of any additive will result in a higher mortality rate of larvae that feed on it.
The bacteria that decompose and process the ingredients into Flake Soil are living organisms, so it is imperative that the Flake Soil is mixed well every 2-3 days is to ensure that fresh oxygen is supplied and incorporated to all parts of the substrate.
It can be difficult to judge the correct moisture level when making flake soil for the first time. If there is too little water, fermentation will not start. If there is too much water, the substrate will simply rot instead of fermenting. Therefore, it is better to add water little by little while mixing instead of adding all of the estimated amount at once.
Flake Soil will continue to ferment very slowly even when it has completed fermentation. Therefore, any extra Flake Soil should be fully dried out when putting it away for storage as the lack of moisture will put a complete stop the fermentation process. When using the dried out flake soil, water can simply be added again up to the correct moisture level before using for larvae.
