Beetle Breeding – Family Cetonidae

Although beetle breeding is not a commonly found hobby in North America, it’s a very popular past time in Europe and Asia. In Japan, many children TV shows such a Digimon and Pokémon base their characters on beetles and other insects. Stores specializing in the culture of beetles exist where hobbyists can purchase everything they need to start breeding beetles at home. Although many families of beetles are found in beetle husbandry, this article will focus mainly on the Cetonidae family, also known as Flower Beetles.

Step 1. Preparing the substrate. Before acquiring your beetles, you should make sure you have the proper material to keep your beetles. Cetonidae beetle larvae require decayed deciduous hardwood material in decomposition. A 20% decayed wood and 80% decayed leafs is required. Such ingredients are commonly found in hardwood forest such as maples, oaks and beech. Coniferous trees such as pine and other “Christmas trees” must be avoided at all cost. These trees contain toxic resin which is deathly once ingested by larvae.

Leaf Litter: Try to avoid newly fallen leafs as they lack the proper state of decomposition and the micro-ecology necessary for the proper the digestion of the decayed matter. The best time to collect your leaf litter is before the fall of the tree leaves which is late summer / early fall. It is even better if you can collect tree leaves which have been decomposing for a few years already. With the help of a light shovel, you can scrape and collect the leaves until you reach the hardened floor of the forest.

Decayed wood: As with the decayed leaves, the wood must be properly aged before it is given to the larvae. Fresh wood is useless and will not be consumed. Rule of thump to decide if the wood is of proper consistency: the decayed wood must be able to be chipped apart with a spade or even better, be able to be torn apart with your hands. Before you render it to proper size with a garden shredder, it is better to break it apart into smaller chunks. Unlike other beetle species which sustains mostly on a wood diet, I personally feel that the degree of decay is unimportant for flower beetles as long as break apart easily.

Preparation: Although you can use a common weed whacker to break down both your leaf and wood material, the best tool I have found is the use of a garden shredder. You just need to slowly add the leaves and decayed wood in small quantity at a time so as to not jam up the mechanism. The use of protective goggles is highly advised. Another tool that is successful is a leaf blower inverted to vacuum in the leaf instead of blowing it and in the process, shred the leaf to proper consistency. This technique only works for decayed leaves and free of hard branches which might damage the blower. Once mixed, the substrate should have a healthy “Earthy” smell. Water might be added in if the humidity is not adequate. To test the proper humidity level, take a handful of substrate and squeeze it hard. If it remains a clump for a second before breaking up then humidity level is adequate. If you squeeze the clump and water is squeezed out then you risk killing your larvae.

Sterilizing: Many literatures suggest you sterilize your substrate before using either by heating, water soaking or even microwaving it. Although smaller invertebrates such as spiders and centipedes may be present in the leaf and wood material, most will be eliminated during the mulching phase. Others who survive this phase are mostly harmless to your beetle larvae due to the large size the larvae acquire. The other drawback of sterilization is the elimination of beneficiary bacterial culture present which is a necessity for the development of your larvae.

Step 2. Acquiring your beetles. One reason why beetle breeding has not taken off in countries outside of Europe and Asia is the strict governmental regulations about importing exotic insects. The Asian Longhorn beetle (Anoplophora glabripennis), although accidentally introduced in wooden crates from Asia and not a direct result of beetle hobby, has become a major pest in the United States and Canada. If you live in these countries, please inquire with your local law agency before ordering exotic insects. If you don’t have any experience with beetle husbandry, I suggest you start off with the smaller species such as Eudicella sp or Pachnoda sp. They have shorter life cycle from egg to adult (about six months) and are good beginner species. The larger species take about one year to complete the cycle and may require more attention from the breeder. You can find beetle larvae and imago stage in various forums and classified pages which specialize in beetle breeding.

Larvae: Before ordering, try to find if other dealers offer the same species at lower price. Beetles procreate at a very fast pace and the Law of Supply and Demand can vary extremely fast from year to year. Rare species may be offered at exorbitant price until it is found in many breeders’ hand and the price reaches a more affordable price the following year. Once you have found a source which offers larvae, try to acquire them at the youngest age as possible (preferably L1). Unless ordering from a reputable breeder, larvae can be exposed to unnecessary stresses such as temperature and lack of nutrients which the buyer is unaware of. This will result in smaller adult or even the lost of the larva. Weaker larvae may not have the necessary energy to complete its final cocoon prior to changing into an imago. Death usually follows such condition. It is also cheaper to procure beetles in larva stage then adult stage.

Imago (adult): As in the case of ordering beetles in larval form, the buyer should acquire young adults which are of no less then a few weeks old. The imago must be active and able to feed. Extreme caution must be taken when ordering adult beetles. Many dealers (not all) from Africa will offer wild caught beetles but are in fact scammers, waiting for you to send them money first before sending you beetles. If the price is too good to be true, it probably is. Upon reception, if your beetles show sign of lethargy, broken tarsi (legs) and scratched elytras, these may tell you that your beetle may have lived a long life already. There is a generation description terminology widely accepted by breeders. A WC term represents a Wild Caught specimen. A WF1 is the descendant of WC. A F1 is the descendant of WF1. A F2 is the descendant of F1 and etc…

Step 3. Keeping your adult beetles.

Preparing the breeding tank:Before releasing your adult beetles in a tank, it is necessary to prepare the proper breeding container first. An old fish tank or a large plastic storage box is a perfect container to keep your beetles. But please make sure that you have proper aeration in the container. Modification to the plastic box lid with window mesh may be necessary. For smaller and medium size species such as Eudicella sp. and Mecynorhina sp., a substrate depth of 15-25 cm would be enough. For larger species such as Goliathus (which will be featured in a feature article), I recommend a depth of 30-50 cm. I also compact the bottom 30% of the substrate into a harder layer. Some species such as Goliathus prefer to lay their eggs in a harder substrate and others don’t mind ovipositing in a looser substrate. It is also recommended that you burry a small wooden branch/log in the substrate as some species seem to prefer depositing their eggs near them. This may simulate in nature the need to lay their eggs near trees and the wooden branches may be thought of as “tree roots.” In addition, small branches must be added to the tank. This allows any beetle that has been flipped on its back side to grab onto something to help it turn right side up. A beetle that has turned upside down may struggle for hours until it dies of exhaustion.

Feeding: In Asian countries, you can buy fruit based beetle jellies. Some are specialized with protein to increase egg production. However they are expensive to purchase outside of these countries. Fortunately, fruit beetles will accept any soft fruits such as banana (the most commonly used), papaya and cantaloupe. The fruit can be served in a bowl that is not too deep as the beetle may not be able to climb back out. I have used ashtrays with success and they are available at your local dollar store. Citrus fruit are not recommended. The fruits should be changed at the first sign of molding. Although I have never read any concrete studies showing that adding protein to the diet of beetles has increased their egg production, I have sprinkled fish food flakes on the surface of the fruits given to my beetles. I figure thousands of Japanese can’t be wrong! The disadvantage of feeding your beetles with fruits is the appearance of fruit flies. If not kept in check, the flies will invade your breeding room. Frequent change of the food source will solve the problem. Another solution is to make your own non-fruit based beetle food. A fellow breeder has shown me the use of sugar base syrup with was fed to his insects with the help of a sponge. The beetle would lick the sponge until the liquid has all been absorbed. I have in turn have used his recipe to make a home make jelly which is readily accepted by my beetles.

Sugar Base Homemade Jelly

  • 200 ml of brown sugar
  • 800 ml of water
  • 1 Tbsp of agar agar (gelling agent derived from seaweed)

Add sugar to water in a cooking pot. Bring water to boil and stir well to melt all the sugar. Once sugar has melted, add the agar agar to pot and stir. Turn off heat and let mixture sit for a few minutes. The liquid will have a slight syrupy consistency at this point. Pour mix in ice cube trays and let sit at room temperature. Once syrup has cooled down, it will jellify and you may remove the cubes from the tray. Store the jelly cubes in the refrigerator and take out whenever necessary.

Temperature: Although most beetles kept in captivity are tropical species, I have kept mine with success at room temperature of 20-25 degrees Celsius (68 – 77 degrees Fahrenheit). Cooler temperature will make your beetles become lethargic and may stop feeding.

Humidity: Although there is no need for your beetle to drink as it consumes all the necessary liquid through the fruits it consumes, your tank should still be at an acceptable humidity. The ideal humidity level would allow you to sustain the proper humidity required as explained under “Decayed Wood” section above. A hand held vaporizer is adequate for the job. However, when you will have several breeding tanks to vaporize, you may want to save yourself a Carpel tunnel syndrome and use a pump vaporizer similar to the ones used for spraying insecticide. Please make sure it’s one that has never been used for that purpose however.

Lighting: In addition, you have to keep in mind that flower beetles are diurnal creatures and a source of luminosity is a necessity to simulate sunlight. A neon light is an adequate substitute when left on for 12 hours a day. An incandescent light source may generate too much heat if placed too close to the beetle container. Never expose your beetles to direct sunlight if you keep your beetles in a covered container as it may overheat and kill all your beetles.

Mating: A good female: male ratio is 3:1. Depending on some species, some males are territorial towards other males of their own species. Rule of thumb is that if it has horns, there is a good chance it will show aggressiveness. However, Cetonidae beetles will never engage in violent combats such as Dynastidae beetles where males can literally dismember each other. Flower beetles’ combats are more like shoving matches and push its opponent off a branch or female. The larger the specie of beetle, the longer it may require for a newly emerged female to start lay eggs even though mating occurs on a regular basis. A pair may be encouraged by placing a male on top of a feeding female.

Community tank: Tanks with mixed species of beetles can be very pretty to look at. However, I do not recommend this practice for several reasons: 1. Once larvae are found in the substrate, the breeder will not know the specie it belongs to. 2. If sub-species of the same beetle are kept together, inter-specie breeding may occur. The hybrids are not well accepted in the breeder community as they prefer to sell/trade pure stains. However, hybrids may be of interest for curiosity reason and offer forms and patterns not found in the wild. These strains should be made aware when selling/trading to others or should not leave the breeder’s breeding.

Egg Laying: Egg laying occurs when the female disappears for several days and you see vertical tunnels visible on the surface of the substrate. Different specie will have distinct preference of the substrate level where the female will deposit her eggs. Some will prefer the middle of the substrate whereas others will prefer to lay her eggs at the bottom. When egg laying has started, proper misting of the tank is crucial. If the substrate was left too dry, the water may not be absorbed immediately and the water may seep at the bottom of the tank and drown the eggs. After several weeks, eggs may be retrieved from the tank or left to hatch on its own. The egg resembles small oval rice. It will absorb moisture from its environment and grow larger, whiter and more spherical as well. Incubation usually takes between 2-4 weeks, depending on the size of the beetles. Usually a novice breeder may not have the patience to wait and will dig in the substrate to satisfy his curiosity. This may be done carefully with a tablespoon and sifted gently. Experienced breeders may decide to let Nature take its course and let the eggs hatch in the tank. This method however may not be possible as the larvae of some species (especially the larger ones such as Goliathus and Mecynorhina) have a tendency towards cannibalism and separation is the only way to reduce this behavior.

Larvae rearing: As explained previously, a larva undergoes three instars (molts) during its larva growth: L1, L2 and finally L3. The length of each instar is again closely related to the size of the beetle specie and ranges from a few weeks to several months. On a side note, the width of the head capsule at the L3 stage can be measured with a digital caliper and is a good measurement for the final size of the adult beetle. Each larva can be reared in its own separate container. For smaller species such as Pachnoda, a 1 L. container may suffice whereas for larger specie, 1-2 L. containers with a regular substrate change may be adequate. A favorite container of mine to use is the Mason jar used for pickles. The glass allows you to see the development of the larva. Whenever adding a larva to new substrate or changing an old one with new substrate, you should always include some of its original substrate, whether from the breeding tank or raising container. This is because beneficial bacteria are present in the adult beetles’ waste product and larvae frass (poop). This bacteria culture is needed for the larva to properly digest the substrate. Some breeders include larva frass in the breeding tank to encourage the females to lay eggs. It is a known fact that adding protein supplement, in addition to a high quality substrate, such as dog food and fish flakes increases the size of the larva which results in a bigger adult beetle. This is particularly true for the medium/large beetles such as Chelorrhina and Goliathus. However, once your breeding program includes more species and/or larger population, individually supplementing each larva with a portion of protein supplement becomes tedious and eventually becomes chore. In addition to the extra work, special attention has to be given to the quality of the substrate when following the extra protein diet. The uneaten food eventually attracts mites and other parasites when the substrate is particularly humid. Population explosion of mites frequently happens when the problem arises and is not taken care of. Although a mild infestation is not a concern to the larva, once the population explodes and covers the entire larva, the mites may block the larva’s spiracle (little breathing holes on both sides of the abdomen) and asphyxiate it. Another supplement which can be added, particularly for smaller species such as Pachnoda and Eudicella, is fruit slices such as apple and pear. The fruit will not spoil as fast as dog food and will not attract mites as easily as dog food as well. But care has to be taken nonetheless and uneaten portion be removed and replaced with a fresh piece. Once a larva has reached the L3 instar, you can even sex your larva (with practice) by locating the presence of the Herold organ. This organ becomes eventually the sperm duct in the male beetle and is represented by a small dot near the end of the abdomen.

Pupation: Once a larva has reached its maximum size after a few months of consuming leaf and wood substrate, it is ready to finalize its life cycle. The first sign that a larva is ready for pupation is when it stops eating and turns to a yellowish taint. Some species will show sign of wandering on the surface such as in the case of the Goliathus (which will be addressed in an article of its own) and a loss of weight. It is crucial that the container which the larva is living in not to be disturbed at this point. The larva will crawl deep in the substrate and construct its pupal cell. The cell consists of basically a mix of particles from the substrate and a bonding substance produced by the larva. Once hardened, the cell becomes waterproof and protects the larva inside. When the larval cell is completed, the larva undergoes the pre-pupa state where it coils into a C-shape, becomes wrinkled, turns in a yellow color and the claws bends into an unusable state. It is important to comment that if you breach a small hole in the cell, the larva may or may not have the necessary energy to repair the cell. This is based on how close it is of the pre-pupa state. If it’s early enough then you are lucky and the larva will repair the gap. If it’s too close to the pre-pupa state or the hole too big, the larva will escape its completed (but damaged) cell and die to the lack of energy to repair or create another cell. If it’s already in pre-pupa state then the larva will be unaware of the damage and continue its metamorphosis. An interesting observation is that 75% of your beetles will actually form its cell against the wall of the container. Thus if you have a glass jar, you’ll have a front row seat to observe the complete transformation to its imago form. The pre-pupa state lasts for a few weeks and eventually undergoes to its final state, the pupa state. The pupa state is a mix between its larval form and its final imago form. The pupa form will have an orange color and will be active within its cell as it wiggles around. This final pupa state will last several weeks depending on the size of the specie. Once emerged, the adult beetle may be taken out of the cell for examination (well…mostly due to beginners’ excitement) but must be buried under a layer of fresh substrate after and left alone. The beetle will climb out by itself once it is ready and begin its adult beetle life. If you decide to let the beetle emerge from its cell by itself, you must make sure that the humidity level is kept constant. A dried out cell becomes hard and will be difficult for the imago to pierce its way through. Once the metamorphosis is complete, the imago will rest. The period will range from a few weeks to several months as in the case of the Goliathus before it is truly ready to emerge from its cell.


Mites (Acarina): All breeders who experiment with protein additive will have to encounter mites at some point in time. They look like little yellow nodules that conglomerate in little groups all over the larva. Although harmless in small numbers, the problem occurs when there is uneaten pet food and a humid substrate. If unattended, the mite population will explode exponentially and completely cover your larva. The mites will block the larva’s spiracle and kill the larva. You must then completely replace your substrate with fresh substrate. For larger species such as Goliathus, I have had good result by gently rubbing the larva with wet fingers. For smaller species, you can place the infested larva in a dry environment for 12-24 hours. The mites require a wet environment to survive and prolonged exposure to a dry substrate will kill most of them. The breeder should return the larva as soon as the treatment is over as this dryness also causes unnecessary stress to the larva. There is another technique to completely remove the mites from your larva. However, this method requires that the larva has not reached the third L3 instar yet and vigilance is required from the breeder. You must observe the larva for signs of molting (either L1 to L2 or L2 to L3). As soon as the molt occurs, you must remove the newly molted larva from its substrate and place it a fresh substrate as the mites will not have time to migrate back to the larva.

Nematodes: These tiny worms are found in soil and are most likely introduced when collecting leafy material for your substrate. As with mites, they enjoy wet environment and love uneaten dog food. Although not known to cause any harms to your larvae, it is quite disturbing when you open a jar and instead of seeing your larva, you are welcomed by hundreds of worms crawling on the surface. The treatment is to replace the substrate with fresh substrate.

Fungus gnats: The fungus gnat resembles small flies. They lay their eggs in vegetative litter such as found on forest floor (also a desired material by the breeder). Once hatched, they swarm your breeding room and can even make breathing (for the human) difficult if you don’t want to swallow any. Rolls of sticky fly tapes hung from the ceiling will usually solve the problem.

Fruit flies (Drosophila): These flies occur when fresh fruit (especially banana) is given to the beetles. They can breed at an extremely fast pace and the fly maggots will spoil the fruits faster. Regular change of the food source will keep the population in check and using jelly will eliminate the problem. As with the fungus gnats, rolls of sticky fly tapes will trap many of the adults. Quickly inserting a vacuum hose in the breeding tank will also eliminate many flies as clouds of fly will take off from the fruit. Extreme care must be taken not to “suck in” your precious beetles.