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

BY:  C. CAMPBELL

(page 5)

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(h - larvae present and growing)

When you find that you have larvae in the substrate, be very careful in handling them.  If they appear to very newly hatched and have heads that are very large in relation to their bodies, it is best to let them grow for a week or two before attempting to move them (if you intend to separate them into individual rearing containers).

Once the larvae have reached body proportions comparable to that of the early 1st instar larva shown at right (fig. 27), you can safely transfer them into other containers of substrate.

Early 1st instar Chalcosoma caucasus larva - Image  C. Campbell
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Fig. 27:  An early 1st instar C. caucasus larva.  Measurement is shown in millimeters.

 
Fungal myceia in rearing terrarium - Image  C. Campbell
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Fig. 28:  An outgrowth of fungal mycelia in a larval rearing terrarium.  Wood fungi are a normal factor in rearing substrate, and their presence are not generally a reason for concern.  There are certain parasitic species of fungi known to attack scarab larvae.  However, they occur only very rarely, and so long as you make regular substrate changes, they should never become a problem.
Most hobbyists prefer to separate out the larvae of larger scarab species for two reasons:

(a) To prevent the cannibalization that can occur in some species.

(b) To ensure that the larva doesn't have to compete with any other larvae for food resources, and thus reaches its maximum growth potential.  However, so long as an adequate amount of food is provided, some species actually appear to grow better when reared together.


 
Before you place the larva(e) into a new container(s) of substrate, there are a few simple things that you should do to the substrate to get it prepared.  Some of the breeding terrarium's substrate (1 metric cup should suffice) should be mixed into the substrate of the new rearing container in order to "seed" it with any beneficial bacteria that may be present in the waste product of the adult beetles.

Without these bacteria, the larvae may possibly not be able to digest food properly, and will thus not be capable of reaching maximum growth.  In the wild, although many scarab larvae live inside decaying logs where they feed mostly upon wood, or in compost piles where they feed on decayed leaves and other plant material, they also eat a lot of other things that they encounter such as the fruits of fungus.  Also, a few species have been observed eating the larvae of other beetles as well as other small arthropods.

Scarab larvae grow by means of 3 larval stages, called "instars".  Each time an instar is complete, the larva sheds its skin and head shield to reveal a new, larger one beneath it.  If high protein foods, along with a rich substrate of decayed wood and leaves are not given to larvae during ALL of their instars, maximum growth potential will usually not be reached.  Thus it is very important that you replace portions of the rearing substrate as it becomes broken down by the feeding activity of the larva.  The intervals at which you change out the substrate will of course vary depending on the amount of larvae you are rearing within a container, the size of the container, and the size of the larva(e).  Let us use the larva of Chalcosoma caucasus (a large rhinoceros beetle of Malaysia) as an example.  By the time that a C. caucasus larva reaches the mid-point in the 2nd instar stage, if you are growing it in a container of substrate measuring about 12" X 8" X 8" (30.5 X 20.5 X 20.5 cm) you would likely need to do a change of substrate about every 8 weeks.

Plastic rearing box for scarab larvae - Image  C. Campbell
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Fig. 29:  A typical plastic rearing box used for the development of a single large scarab larva.  This is the size and model which I used at my workplace to rear the larvae of C. caucasus, and it measures 12" X 8" X 8" (30.5 X 20.5 X 20.5 cm) in size.  Popular terraria such as these are sold in various sizes at most larger pet stores for the containment of lizards, frogs, salamanders and any other small animal that requires the kind of moist habitat which can easily be maintained within such a container.  Creating and maintaining appropriate moisture levels within a box such as this is relatively easy (see photo below).
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Plastic rearing box for scarab larvae - Image  C. Campbell
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Fig. 30:  The same rearing box with the lid removed.  The lids of these types of boxes have far too much ventilation to be suitable for proper maintenance of the humidity level required for beetle rearing substrate, so about 90% of the box has been covered with a plastic bag.  The lid is then snapped back down over the plastic.  Using the plastic cover to retain moisture allows for periodic adjustment depending on the amount of moisture you wish to keep inside or release from the container.  If the substrate appears too saturated, just fold back the plastic somewhat for several days to allow extra evaporation.  Folding it back so that 50% of the lid is ventilated should work in most instances.  However, always be sure that at least 10% of the lid space remains open at all times, so as to allow for an exchange of air.

 
 -Developmental stages of the Chalcosoma caucasus larva -

 
Early 1st instar Chalcosoma caucasus larva - Image  C. Campbell
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Fig. 31:  Early 1st instar.
Late 1st instar Chalcosoma caucasus larva - Image  C. Campbell
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Fig. 32: Late 3rd instar.

 
Early 2nd instar Chalcosoma caucasus larva - Image  C. Campbell
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Fig. 33: Early 2nd instar.
Late 2nd instar Chalcosoma caucasus larva - Image  C. Campbell
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Fig. 34: Late 2nd instar.

 
Early 3rd instar Chalcosoma caucasus larva - Image  C. Campbell
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Fig. 35: Early 3rd instar.
Late 3rd instar Chalcosoma caucasus larva - Image  C. Campbell
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Fig. 36: Late 3rd instar.
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