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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 4)

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Small pressure sprayer for moistening terraria - Image  C. Campbell
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Fig. 22:  A small 2.5 pint (1.18 liter) pressure sprayer which is useful for regulating the moisture level of terrarium substrate.  Most models have an adjustable nozzle which will allow you to find a misting setting which works well for your particular situation.
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Rearing substrate - Image  C. Campbell
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Fig. 23:  Rearing substrate which is of just the right moisture level for rearing scarab beetles.  The substrate should be carefully monitored for signs of desiccation on a regular basis, and should be kept moist at all times through all life stages.
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Close-up of rearing substrate - Image  C. Campbell
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Fig. 24:  A close-up view of the rearing substrate.  Be careful not over moisten your substrate, as one which is too wet can be just as inappropriate as one which is too dry. 
(c - temperature for the breeding / rearing terraria)

Most tropical scarab species do best at a temperature of between 75-85 degrees Fahrenheit (24-29.5 degrees Celsius).  Keeping them too cold will either make them sluggish or even kill them, because their metabolic processes won't work properly at lower temperatures.  They are exothermic (cold-blooded) animals, and their body temperature stays at approximately the same temperature as their surrounding environment.  For species from cooler parts of the world such as North America, the temperature can be allowed to drop lower than 75 degrees Fahrenheit at times, and in fact some species which come from high elevation forests in cooler climates need a seasonal variation in temperature to properly complete their life cycle.
 

(d - lighting)

Having an overhead fluorescent tube light for your breeding terrarium can be helpful in encouraging normal breeding activity in some varieties of scarabs, most notably, the cetoniines (flower beetles), which are active by day.  Direct lighting is not considered to be very important for dynastine scarabs (rhinoceros beetles) which are mainly active at night.  Also, it is not necessary to light terraria which are for growing larvae only, as the larvae live buried in the substrate, and thus lighting is of no significance to them.
 

(e - humidity)

The substrate should be kept moist, but certainly not soaking.  A pressure sprayer is useful for maintaining the balance of moisture in your breeding / rearing terraria.  Various sizes of these devices can be purchased in the gardening section of most hardware or department stores.  If you have many terraria to spray regularly, get a 2 gallon (7.60 liter) model.  If you have only a few terraria, a smaller size sprayer such as the one shown in the photo (fig. 22) will suffice.  Whatever you use for spraying water in your terraria, make sure that the vessel has not ever been previously used for spraying insecticide or any other chemical which may have left residues that could prove harmful to your beetles.  The substrate should be somewhat damp to the touch (see figs. 23 & 24), but if you can squeeze a clump of it in your fist and get water to run out of it very freely, it is probably too wet.


 
In general, spray the surface of your substrate when it starts to look rather dry.  A hard crust may form on the surface which can be rather misleading.  This crust can conceal a very most layer just beneath the surface, so always break this crust first to make sure that you aren't actually moistening a substrate that is already moist.
 

(f - feeding (adult beetles))

Most cetoniine and dynastine scarabs will happily accept soft fruits such as banana in captivity.  A few species like pear or apple.


 
Give them a fresh, adequately sized slice of such fruit each day if you can.  Every 48 hours will suffice, but feeding them a fresh piece each day is recommended because the beetles tend to make a pulpy mess of the fruit, and it starts spoiling VERY fast in the high humidity of the breeding terrarium.  To supplement the beetles with any protein requirements they may have, you can sprinkle a quantity of ordinary flake fish food on the surface of the banana slice or other fruit.  Also, some species will eat apple sauce, again with fish flake fish food mixed in for nutritional enrichment.  This can be a much less expensive alternative to fresh fruit if economy is an issue.  Slight misting of the terrarium and beetles occasionally will supply moisture needs for both the insects and the substrate.  Just mist the terrarium if the environment starts to look a bit dry.
 

(g - first appearance of eggs and young larvae)

If you start out working with adult beetles as opposed to larvae, and have prepared your substrate and breeding terrarium as I have indicated, you should start seeing eggs or young larvae within a short time.  Usually, you can get your beetles to deposit eggs within just a few weeks of having introduced them to the terrarium.  Mating  (see fig 25) may be observed almost immediately, but the females may take some time before actually starting to lay eggs.  A few weeks or even a few months are sometimes needed before egg laying, or "oviposition" starts taking place.

Chalcosoma caucasus (mating) - Image  C. Campbell
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Fig. 25:  A mating pair of C. caucasus.  Actual mating in this and most other species of scarabs can take between 10-20 minutes.  Mating beetles are often rather difficult to disturb, and generally will take little notice of movement in and around their terrarium.  Using their highly sensitive lamellate antennae, males locate females by the pheromones which they emit.  Like most other arthropods, scarabs utilize a specialized structure called a "spermatophore" for the transfer of spermatozoa.  This structure is simply a sealed packet of spermatozoa which has a tough yet flexible outer layer.  Male dynastines sometimes deposit spermatophores on the substrate surface as they produce them, especially if they do not have access to mates.  After mating, the female may not necessarily deposit her eggs immediately.  Time is needed for her eggs to become fertile.  Dynastine species such as Chalcosoma burrow deep into the substrate to oviposit, whereas many cetoniines simply deposit their eggs nearer to the surface.

 
The female beetles may burrow deep into the substrate to lay eggs, or may deposit them near the surface, depending on species.  Large types, such as those in the subfamily dynastinae, nearly always oviposit their eggs very near the bottom of the substrate.  As always, the substrate surface will need to be misted occasionally to prevent the lower layers from drying out.  The amount of misting will vary depending on the humidity of the air in the room, but usually it will need to be done every two or three days if the humidity is low.  Avoid over watering, otherwise the lower substrate can become rather saturated, even when the surface appears quite dry.  Over watering can prove fatal to the eggs.  Continue to make sure that the adult beetles are given fruit as needed, at a frequency of at least every two days, or daily if possible.

 
Newly hatched Chalcosoma caucasus larva and egg - Image  C. Campbell
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Fig. 26:  A newly hatched C. caucasus larva and un-hatched egg shown beside a US 25 cent piece.  Larvae this young are extremely susceptible to damage, and should not be handled directly.  If moving sensitive larvae or eggs such as these is for some reason necessary, do so by scooping up the substrate upon which they are resting, rather than attempting to pick up the larva or egg itself.  Also use extreme care when covering them back over with substrate.  The larva shown is called the "1st instar", and through the course of its development, it will increase in size and weight by hundreds of times.
A few weeks after introducing the beetles to the substrate, you can very carefully dig down into the substrate and check for the presence of eggs or young larvae.  Cetoniine scarabs tend to deposit eggs in the upper and middle layers of substrate, although this is not  always the case with some of the larger species.  Because the dynastines oviposit near the bottom, it is often best to not disturb this area for a considerable time, 6 -8 weeks in some cases.  The eggs are quite delicate, and often susceptible to rupture if handled.  It is important to move the substrate around quite gently, as the eggs and young larvae are easily injured.  At this point in time, the larvae would likely still be quite small if present at all.  Again, keep in mind that it may take as long as 6-8 weeks before any larvae appear, as the oviposition +egg incubation period varies depending on the species.  Bear in mind also that the beetles may not necessarily begin laying eggs immediately after mating.  The eggs of course vary in size depending upon species, up to 1/4 of an inch (6.35 mm) in the case of large rhinoceros beetles such as Chalcosoma, and are generally light in color.  Continue feeding and maintaining the adult beetles as always.
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