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CAPTIVE BREEDING MANUAL FOR BEETLES OF THE FAMILY SCARABAEIDAE,  SUBFAMILIES CETONIINAE (FLOWER BEETLES) AND DYNASTINAE (RHINOCEROS BEETLES)

BY:  C. CAMPBELL
LAST REVISION - Feb. 27, 2002

NOTE:  The author of this site is not a supplier of beetle specimens, living or preserved.  All of my personal beetle photos (both native and exotic species) were made during the years that I was employed at a public insectarium.

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Breeding Scarab beetles -

The captive breeding of scarab beetles of the families cetoniinae and dynastinae will be discussed in this online manual.  There is a general technique for rearing such beetles which involves creation of a rearing substrate consisting of two basic materials:  wood mulch and leaf mulch.  The process for creating these two substrate components will be described early on in the manual.  The manual is divided into two sections.  Section 1 concerns mainly the procurement and preparation of the materials you will use to create your rearing substrate, and section 2 deals with the actual biology and life cycle of the beetles themselves.  The mulch ratios and extra additives used in the final substrate mixture will vary depending upon the species you wish to rear, and all beetle hobbyists have their own personal variations and techniques of using it.  I would like to point out that the rearing of scarab beetles is by no means an easy thing to teach someone, and it is actually a skill which must be learned by personal experience.  To become a real master of scarab beetle propagation, one must often work at it for many years as one would for a hobby such as exotic plant culture.  In time, you will develop an innate sense about things such as substrate quality, and will be able to determine its precise moisture level and consistency just by touching, smelling, and looking at it.  The sequential instructions presented in this manual however, will give you a good head start about what to do.

(note:  If you are seeking information specifically about Goliathus, please refer to the Goliathus manual for breeding/rearing info on such.  Also, you can read an excellent article by beetle hobbyist Yasuhiko Kasahara about the captive breeding of Dynastes hercules here.)


 
Section 1 -  Substrate collection and preparation:
 

Before you even obtain some pairs of adult scarabs for breeding, it is always a good idea to at least have the materials prepared that will be used to create the rearing substrate.  The materials used to rear beetles of the subfamilies cetoniinae and dynastinae are heavily decomposed deciduous hardwoods and old leaf litter that has aged to the point that it has become a bit soft and moldy.  When found in nature, these two materials are very seldom of the proper consistency for ideal use as a rearing substrate for captive beetles, and they usually must be broken down further.  So, the first section of this manual will be concerned with explaining the methods by which one actually prepares these two materials, and uses them to create the rearing substrate which is the very foundation of captive scarab breeding.
 

(a - collection of the substrate materials)

Obviously, the first thing you need to do is locate some sources of decayed wood and leaves.  If you have access to some deciduous hardwood forest or woodland (see figures 1 & 2 at right), that will certainly be one of the best places to look for what you need.

Deciduous hardwood forest, United States - Image  C. Campbell
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Deciduous hardwood forest, United States - Image  C. Campbell
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Figures 1 & 2:  Shown above are some examples of the sort of deciduous hardwood forest that are excellent places to find a ready supply of very old, decayed logs and leaves.  From these materials you can create the mulches which will form the basic components of your scarab beetle rearing substrate.

 
Decayed log - Image  C. Campbell
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Fig. 3:  Here is an extremely old Oak (Quercus) log which is in the advanced state of decomposition ideal for creating wood mulch for beetles.  The wood has become yellow-white with age, is very brittle, and is easily crushed with bare hands.
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Decayed stump - Image  C. Campbell
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Fig. 4:  In this instance, the decayed wood is a stump rather than a fallen log.  Note that the color of the wood is of a rusty brown hue.  Often, you will be able to determine if a log or stump is at the proper state of decay just by looking at it.  This stump is infiltrated by the burrows of many beetle larvae and other insects, and the mushrooms of  wood fungi are present on the bark.
Note:  If you live in a part of the world where venomous snakes and spiders are common, use caution when exploring a wooded area.

For the wood, what you'll be looking for are rotten, decomposing logs and stumps of deciduous hardwood trees.  These are non-coniferous trees which shed their leaves each year, and have wood which is quite hard when in the living state, hence their name.  A large hardwood log lying on the forest floor can take upwards of 10-15 years to become aged to the point that it will make an attractive food for scarab beetle larvae.  Wood that is fresh is completely useless.  Even an old hardwood log can be difficult to break into pieces of a manageable size to transport home, so it's a good idea to bring some strong tools to break up logs.  Fungal action is the decomposing agent that makes these logs suitable as a component for rearing substrate.  When the spore (microscopic seed) of a species of wood-eating fungus lands on a log which is of proper age and moisture content, it starts sending out tiny roots called mycelia.  Over many years, these mycelia spread and gradually party digest the hard cellulose of which the log is made.  In time, the log is transformed from a very solid wood to one that is very soft and crumbly.  In addition to the fungus, there are other living things which help get the log into a condition appropriate for your use.  Ants, termites, and the larvae of many beetles and other invertebrates all take up residence inside logs and dead stumps once fungal transformation has begun, and further aid in breaking down the wood into a suitable, crumbling consistency.  One of the very best varieties of decomposing wood and leaves to use is that of Oak trees (Quercus spp.).  Also, that from Beech (Fagus spp.) is very suitable.


 
Decayed stump - Image  C. Campbell
Decayed log - Image  C. Campbell
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Figs. 5 & 6:  Some further examples of well decayed wood that is suitable to be made into rearing mulch.  If a log readily shatters to the core when given a hard kick, it's definitely at the right level of decomposition to serve your purpose.  For logs and stumps that are well decayed on the inside yet retain a hard outer layer of wood, a sledgehammer or pickax will prove useful in breaking the wood up into more manageable pieces. 

 
In general, decomposing material from all species of deciduous hardwood trees can be used, but one should generally avoid the use of coniferous (needle-leafed) trees such as Pine (Pinus) and Cypress (Cupressus).  The reason is because the wood of these trees contain resin and oils which are toxic to scarab beetle larvae.  Thus, the many commercially available forest products such as pine bark mulch and cypress wood mulch are quite useless to the beetle hobby.  If you live in an area of very old growth coniferous forest, and find a log which has obviously been decomposing for an extremely long time and has become exceptionally soft and crumbling, it can be used so long as you cannot detect any resin smell upon close examination.  If it has a strong fungal smell when moistened, then you can be reasonably sure that it has reached a stage of decomposition that would make it suitable for scarab beetle larvae.  The main concern with coniferous wood lies with the presence of resin.  Very old and rotten conifer logs and stumps lack this compound, as it gradually evaporates out of the wood during the decomposition process.
Shelf fungi on a decaying log - Image  C. Campbell
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Fig. 7:  A huge and very old Cottonwood (Populus) log whose degenerative state is not especially apparent from an external point of view.  However, there is a lot going on inside it, as is evidenced by the numerous mushrooms of "shelf" fungi which have sprouted from its sides.  Shelf fungi are one of the most commonly encountered varieties of wood-eating fungi in the woodlands of North America.  Given time for a bit more decay, a decomposing log of this size will yield a vast supply of rotted wood for use in beetle breeding.

 
It does take many years for this to occur, however, so only use conifer wood which you are quite sure is extremely old and decomposed.  Some types of conifer wood, such as Cedar (Cedrus) never really become suitable for use, as their wood is so dense and strong that it can withstand the forces of decay for many decades, remaining completely hard and intact.

If you can get access to fine shavings or sawdust from hardwood trees however, that would be suitable, but it would still be fresh and un-decomposed, and some alteration would be necessary using commercially available fungal cultures.  Making your own decomposed wood using fungi is a process complex enough to warrant its own section in this manual, and so it will be discussed at some point in the future after I have gained experience with it.  For now, I will continue to describe the means by which one makes rearing substrate by simply using materials gathered from nature itself.


 
Compost pile - Image  C. Campbell
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Fig. 8:  A typical compost pile, consisting primarily of layers of leaves, grass clippings, and various other plant materials.  A compost pile can be a convenient way of maintaining a ready supply of decayed leaves throughout the year.  The feeding activity of bacteria and many other small organisms all help to party break down the leaves and get them into a condition suitable for creating the decayed leaf mulch which is one of the two main components of scarab rearing substrate.  An added bonus of a compost pile is that by creating such an accumulation of plant material, you can often attract the native scarab beetles which you may find interesting to captive rear.
As for the decomposing leaves, I think you'll find this a much easier material to find and collect.  Deciduous hardwood trees such as Oak (Quercus), Beech (Fagus), Elm (Ulmus), Maple (Acer) and many others are all suitable.  It is best to use leaves from species which have rather large leaves, because this will end up amounting to a greater quantity of the leaf mulch which will be created from them.  It is possible to use rather freshly fallen leaves once they have been on the ground for several months, but if you can get leaves that have been "composting" for a couple of years and have obvious signs of decay, that will be even better.  To quickly gather old leaves for transport, I just rake them into large piles and then stuff them into ordinary plastic garbage bags, compressing them periodically.  To always have a ready supply of decomposing leaves year-round, you might want to consider creating a special compost pile for leaves only.  A small space enclosed with fencing or wooden panels will work well for this purpose.  All you need to do is keep the leaves in a somewhat sheltered area to prevent them from being blown away in the wind.  See the example in the photo at left (fig. 8).
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Forward to page 2 of the breeding manual

 
introduction page


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