Thursday, 18 June 2015

A brief (and hopefully) comprehensive guide to the substrates for rearing larvae of flower, rhino and stag beetles

When I was starting with  beetles, I had trouble with finding info about what kind of substrate is suitable for different sorts of beetles. The things were further complicated by information obtained from various beetle "keepers" enthusiasts which used different substrates to raise same species of beetles.  Since I am often being asked similar questions, I have decided to break down this information in one post. This information is mainly based on my own knowledge/experience and presented in a very shortened generalized form, and thus may not be suitable for some specific beetles. However, most likely it will suit very common groups of beetles and the post could particularly be helpful for beginners.
There are 3 most popular groups of beetles which are kept by breeders. 
These are flower beetles (family of scarab beetles, Scarabaeoidea, subfamily Cetoniinae; such as Pachnoda ssp, Dicronorrhina ssp or Mecynorrhina ssp), rhino beetles (family of scarab beetles, Scarabaeoidea, subfamily Cetoniinae, Dynastinae; such as Megasoma ssp or Dynastes ssp), and stag beetles (family Lucanidae, such as Lucanus ssp or Dorcus ssp). 
The development of larvae of all these groups in nature is usually attributed with decaying organics, mainly rotting wood.  However, in captivity many breeders often grow major adults using leaf litter or leaf litter mixed with decayed wood as the main substrate. It is also generally accepted that the simplest substrate is the one consisting of decayed leaves and wood of hardwood trees such as oak or beech. Therefore "the basic" substrates are:

1) Pure leaf litter. 

This substrate normally consists of a lower layer of partially disintegrated decayed leaves which could be mixed with some woodland top soil (humus).  The leaves should be well decayed, not freshly fallen, preferably at least 1 year old. In such substrate, hard parts of leaves are pre-digested by microorganisms. The presence of soil in such substrate could help distributing the moisture and developing of the beneficial bacteria, particularly if a container with larvae is not very deep. 
This substrate is good for any flower beetle larvae, although some species may require some additional protein supplement during their later stages, e.g. starting from the late L2-early L3. Some beetles such as goliath beetles, starting from L2 stage require mainly high protein food, and almost do not consume any other substrate. 
This substrate is also used by many breeders for raising larvae of some rhino beetles, particularly of megasoma ssp.  

2) Pure decayed (rotten) wood.
This is normally pure rotten wood from hardwood trees (oak or beech are always preferred), which ranges from soft white to brownish/black in colour and either soft or just soft, but not hard wood. The soft wood is that kind that you can easily brake and crumble it with your hands, the "just soft" wood is that kind that it is difficult to brake it with your bare hands, but it would be very easy to hammer the nail in. This wood is usually the result of part of the tree being damaged by fungi and in such wood the most of the lignin is destroyed either by fungal and/or bacterial activity. The softer wood can be used for rhino beetle substrate and for oviposition of majority stag beetles such as lucanus, although the "just soft" wood could be also good for the some other stag beetles such as dorcus or phalacrognathus. Both types of wood could be mulched and used as food for both stag and rhino beetles right away, although the majority of stag beetles may prefer the harder ("just soft") decayed wood.  Since the nutritional value of freshly decayed wood is not exceptionally high, some additives such as soy protein powder or dog food pellets are often recommended, particularly at later stages of the larvae development. The decayed wood which you can find inside of large dead oak trees and which has pure brown colour and feels like a cork is not suitable, as in such wood all nutrients such as cellulose are already disintegrated.

3) Decayed wood and leaf mixture.

This is normally the mixture of mulched decayed wood and leaf litter mixed together. Stag beetles normally do not grow well in "leafy" substrate and require decayed wood or more advanced substrate for their growth.  This substrate, however, works quite well for many rhino beetles, particularly with some additional protein supplements starting from the early L3 larvae. In my experience the early larvae of many rhino beetles grow better in decayed leaf substrate with only little wood in it; then the bigger the larvae may require more wood as they grow. I normally end up with like 40% of the wood in the substrate for the late L3 larvae. All bigger chunks of decayed wood (ideally a log) need to be placed at the bottom of the container so the larvae could easily access it, if they would require more wood.   

Advanced substrates.

1) Fermented wood (flake soil)
In this substrate the harder wood components such as lignin are pre-digested by bacteria. The substrate is normally made using oak wood sawdust/shaving, baking flour and yeasts. The yeasts develop "feeding" on carbohydrates of baking flour and products of the fermentation and create favourable environment for other microorganisms which digest harder components of the wood. Ultimately, the process leads to enriching of the substrate with nitrogen-rich biocompounds that later are assimilated by the larvae. The process is only effective at the temperatures above 20C and in bigger volumes. At 25C using air dried oak sawdust it takes about 2 months to obtain a good substrate for stag beetle larvae  or 3-4 months for rhino beetle larvae.  The ready substrate could be from dark brown to black in colour when moist and should not smell ammonia or alcohol but have rather "earthy" smell. As the composition and degree of wood degradation of fermented substrates obtained from different sources may vary, it is always wise not to replace the existing larvae substrate with a new one right away completely, but to introduce the new substrate gradually. It will help the larvae to develop the culture of their gut bacteria necessary to digest new components of the substrate, otherwise the larvae may suffer/perish from indigestion. The advantage of such substrate is a high availability of the cellulose and nitrogen-rich bacteria/components which promote the larval growth. The fermented substrate for rhino beetles can also be used for flower beetles, although I personally did not find the difference in development between flower beetles larvae growing in fermented wood flakes and in the leaf litter substrate.

"Stag beetle grade" fermented wood flake soil

"Rhino and flower beetle grade" fermented wood flake soil

2) Kinshi
Kinshi is the well developed mycelium of fungi, which is normally grown on oak or beech sawdust/woodflakes. Due to the high nutritional value kinshi represents an excellent substrate for various beetle larvae, particularly some stag beetle larvae such as dorcus or phalacrognathus. Kinshi  can also be given to rhino beetle larvae but only as a part of the substrate. The woodflakes, mixed with some additives such as baking flour, are sterilized, and the mushroom spawn is introduced. It normally takes at least 2-3 months for spawn to completely colonize the substrate. In ready to use kinshi the fungus colonizes almost all free space of the container and the substrate should have a  bright white colour. The most common fungus used for this purpose is king oyster mushroom, pleurotus eryngii,   perhaps because its mycelium develops much quicker than other similar mushrooms. This allows fast colonizing of the substrate, thus decreasing the chance of the  contamination with mold. Another fungus, which is important for the development of some stag beetles such a Allotopus ssp, is turkey tail fungus, trametes versicolor, is often used for making kinshi. The biggest challenge of the kinshi production, particularly the one at home, is a contamination of the substrate by mold which can easily put off  any breeder from making it:(    

kinshi at early stage;  various degrees of colonisation of the substrate can be seen

ready to use kinshi

You can contact me via regarding any related issue  


  1. Thanks for the post, I'm just starting to raise my beetles from L1 larvae to adult beetles so I have a lot of time until then. I want to achieve the most impressive size possible while they are still young, and I love how in depth you are about the chemical details. I've also cultured mushrooms before and can attest to how much of a pain contamination can be, especially common spider mold. I find the only solution to decontamination to be extreme heat from say a steamer and pressure-cooker for sterilization. The spores can be bought really cheaply online. But I would add that you can buy Pre-colonized substrate from Wegmans and online in little kit boxes to save the headache.

    Also, I have found some really rotted wood on the local mountain away from local pesticides and their runoff to a stage of rot that is similar to hard butter. However, I found lots of ants and nematodes in it and decided to pressure cook it and bake the excess moisture from it to serialize it. Is this going to be a problem for the larvae to eat if I killed the local bacteria?

    Again, thanks for the post.

    1. thanks,
      we do not have Wegmans in the UK, so we have to go trough all the pain:)
      regarding pressure cook it, in my opinion it is bad for the substrate, as you will destroy all microorganisms such as natural yeasts, fungi and bacteria that assimilated nitrogen from the substrate. Once they are decomposed, nitrogen based compounds cannot be assimilated from the soil in an easy way. If your larvae are small, I just would mulch it finely and check for the potential predators such as click beetle larvae, or other big bugs. Ants can be a nuisance if they will be able to build up a colony in your substrate, but this rarely happens as there should be a substantial number of them; the smaller things such as nematodes are perfectly fine in substrate with larvae.

    2. You mentioned color as well, and I for got to ask earlier, but what degree of rot is an oak tree that has turned soft and copper colored? Its been hard to find information that describes the stages or tree rot for harvesting substrate.

      I found a number of decayed wood that was black on the surface but looked more like the local maple trees and not the oak I've been looking for. The most common oak tree in the area I looked was chestnut, the rest were mostly either pine or maple, and I understand pine is one of the worst types of wood to use.

      On the matter of yeast, could I just add baking yeast to help? Also, anything you know about adding dog food pellets that reduces the spread of white spider mold, I've already tossed a contaminated batch before because it was colonizing too much of the substrate.

  2. So, about substrate and making it suitable.. I am getting dynastes hercules larvae and I want to make my own substate. I can gather rotted hard wood and a compost soil mixture..but I did read about sterilizing the mixture. I am just afraid anything in the wood could be harmful to the beetle larva. Any suggestions?

  3. So, about substrate and making it suitable.. I am getting dynastes hercules larvae and I want to make my own substate. I can gather rotted hard wood and a compost soil mixture..but I did read about sterilizing the mixture. I am just afraid anything in the wood could be harmful to the beetle larva. Any suggestions?

    1. I use a few methods myself for sterilization that I learned when making mushrooms for the first time where contamination was a big issue. I think all you really want to worry about sterilizing is the rotten wood for "uninvited guest" that may harm your larvae, like mites, ants, and nematodes. The only method I know to use to kill them and their eggs with the possibility of retaining the micro bacteria is to add boiling water to the wood and let it soak for about 20 minutes. depending on how big your chunks of wood are, that should be enough for the heat to kill the buggers off. A bonus is that this method makes breaking apart the wood much easier as the water will soften it significantly. Lastly, you can mix the newly sterilized wood, after draining the excess water, with your untreated compost, provided that it has no pesticides or plant food additives. Never use store bought top-soil, as that stuff is usually collected from the silt layer of bays and rivers where all the sewage and chemical runoff goes. Hopefully your compost should have enough good bacteria to recolonize the wood for you when you mix.

      I hope this helps.

    2. Also, to speed up the grow time, I'm using an aquarium heater to control the substrates optimal growth temp(20c-25c). Keeping the moister of the substrate also helps conduct the heat across the container and keep the larvae from entering hibernation mode this winter. I have a few L3 larvae that will hopefully pupate by the end of November.

  4. Good day, can I use rotten coconut wood as a substrate for breeding?

    1. Hi,
      I have no idea. Never tried it, as we do not have much of it in UK:)
      If I try new substrate I always try it first in a small quantities with only few larvae.

  5. Hi there I'm very new to this and I'd like to ask you where can I get the row material I mean the the oak or hard wood shaving or flake from.and how much would be approximately cost per kg

  6. Normally you need to look for some local woodmills which work with oak or beech and it is normally not expensive. However, the delivery could be very expensive, as it is very bulky, and often sold in bags by volume, since its weight can vary a lot depending how much water it contains. Cannot say anything about the price again, as it can differ massively, e.g. sometimes you can buy ~50-60 L of the oak sawdust including delivery for £30 in the UK. I saw some companies in Denmark selling beech wood shavings basically for nothing. Internet can help sometimes:)

  7. I see.I suppose if you buy from Denmark you have to buy very large volume of it.
    Doas anybody have a recipe to make a nice substrate for Kabutomushi larvae!!!