Larva care: As with all beetles, Goliathus larva undergoes 3 distinct instars: L1, L2 and L3. This can described as the shedding of the old skin. The process starts with the larva refusing to eat for a few days. The shedding begins with a split at the top of its head capsule and eventually splitting the capsule in half. The new instar wiggles its way out of the capsule, leaving its old skin behind. Once shed, the new head capsule is completely white and has not had a chance to harden yet. Handling the larva should be minimized. Within a few hours, the head capsule will turn to an orangey-red, brown and finally black. (Note: Although not verified by myself, some breeders leave the shed skin in the container. The disappearance of the old skin either suggests that it decomposes rapidly or is consumed by the larva, which is a normal behavior in the animal kingdom. )
Newly hatched Goliathus larvae can be kept in a good quality substrate (80% leaf, 20% wood). However, it is best to switch to a protein diet after a week or two in order to obtain larger larvae. Until the next necessary substrate change, the L1 larva can be kept in that substrate for a smoother dietary transition (see Substrate section below). Young larvae (egg-L1) are kept in empty pill containers to observe their development and are transferred to lure boxes (see Keeping and feeding your larvae below) at L2. Once the larva has reached L3, sandwich containers (cheaply available at your local dollar store) are used to rear them. Rubber bands should be used at this point since a large L3 larva can easily lift the lid of the container and escape. You should change the substrate if it starts smelling badly, have mite problems or filled with larva frass (poop). Since an older Goliathus larva does not consume the substrate it lives in, using a smallest possible container is recommend. However, the larva’s living comfort should not be neglected and the larva should still be able to turn around in the container. A smaller container allows the larva to find its protein pellet faster and allows less waste. Once the larva becomes L3, sexing the larva is similar to other Cetonidae species.
I find it extremely fascinating that a larva the size of a Goliathus can reach its maximum size in the span of 6 months before it is ready to pupate. The biggest larva that I was able to rear weighted in at 94 g. which yielded a male of about 90mm. This suggests that the Goliathus larva can grow over 100g since adult males can reach 110mm. You can admire this exploit when you breed other giant beetles such as Dynastes Hercules and Megasomas. Larva development can be as slow as 3 years for some of these species.
Diet: Unlike other Cetonidae species, Goliathus larvae need a high protein diet to grow to maximum size. It is theorize that Goliathus larvae are carnivorous in the wild because a physical difference can be seen between Goliathus and other Cetonidae species. The leg extremity of the Goliathus larva has developed a more pronounced talon than other species which suggest a predacious lifestyle. It may well in fact prey upon other invertebrates found in its environment. I have experimented with most pet foods available on the market and my conclusion for the ideal food that can be given to your larva is fish food flakes and semi-moist cat/dog food. Anything else that is of hard consistency (dog, cat, fish, ferret) is rejected. The food can be deposited on the surface of the substrate and the larva will come to the surface and pull down the flake/pellet. Uneaten food should be removed after a few days as it may attract mites and spoil your substrate.
Fish Flakes: I feed my larvae fish flakes until they reach the last instar. Once L3 stage has been reached, their appetites are enormous. A fish flake diet becomes exorbitant due to its cost. However, fish flakes have the highest protein content of all pet food, some containing as high as 75% crude protein. If you can afford to feed them with flakes throughout their development, it would be the best.
Cannibalistic behavior: It is well documented that Goliathus larvae have a tendency to snack on their siblings. As such, I wanted to know how much truth there was behind it – and also the fact that I was running out of space due to keeping each larva in individual container. So I decided to place 10 newly hatched L1 larvae in a 1 L. container and waited for the result. I continued their daily feeding of protein additive during that time. After two weeks, I decided to verify their development. I observed that more than 50% of the larvae had missing limbs and/or had completely disappeared. Another observation: there were always one or two extra plump larvae amongst the survivors. After this experiment, I decided to slow down on my breeding program and I individually separated each larva.
Techniques to succeed a large breeding program: It was fine and dandy to pamper your larvae on a daily basis when you have a dozen of them, even to the point of giving them individual care. I would sit down for several minutes after adding my protein pellet and waited for the larva come to the surface to grab and pull it under the substrate: that was the first year. (I would often joke that would I sing lullabies to them before going to bed.) For the second generation, I was literally overwhelmed by the quantity of larvae I was raising. So much so that I had to stop the females from ovipositing more eggs. I was getting close to achieving over one hundred larvae. In order to be able to manage my feeding/substrate change schedule (and have a normal life), I came up with as much a “lazy-man” method as possible. I realized that it was quickly become a chore instead of a passion as I was easily spending 45-60 minutes every day on the upkeep of my Goliathus – and that’s after coming back from a regular job, help make supper and putting the kids to bed!
Substrate: Unless you live in Japan where beetle substrate can be bought at your local department store, you have no other choice then to make your own. You have to go in the forest and collect large quantity of dead tree leafs. Even harder is searching the forest floor for fallen tree logs with the proper decay level. And let’s not forget about the strange looks that passers-by give you. (Picture this: Searching a forested area near to a cemetery and I walk out of the woods with a bag on my back and a shovel in my hand…) Once you have the raw ingredients, you have to take the time to process it and shred it to proper consistency. Having said this, your homemade substrate can sometimes be more valuable than the larva itself. So as to facilitate my Goliathus rearing method, I no longer use homemade substrate after the first substrate change. Once the larva has adapted to consume pet food (late L1), it is no longer necessary to use leaf compost because it no longer eats it. This saves you hours of labor to manufacture your substrate. I replace the substrate with 100% peat moss (also known as sphagnum moss) which can be purchased cheaply at your local garden center. Peat moss is basically decomposing sphagnum moss found in bogs and peat lands. It is completely sterile as it is sold in bails of various sizes and with 0% humidity. A light humidification is required before using it for your larvae. A pressure pump vaporizer will humidify your substrate uniformly. Pouring water directly into the peat moss to mix will create clusters of wet peat moss. Once the moisture level is achieved, you should have a very light and well aerated substrate. It is cheap, easy access and makes an ideal substrate for your Goliathus.
Keeping and feeding your larvae: Another time consuming activity is the feeding period. This entails gathering all the containers, opening each individual lid, placing your pet food inside, closing the lid and placing all the containers back. Assuming it takes 2 minutes each, the time spent on feeding each of your larva is considerable when you feed a large population. And that is not considering substrate change when it has been soiled by uneaten food or mites. You can easily add another 2-3 minutes to each larva. I know this sound very much like micro-management but you have to look at the larger picture when rearing a large population. As a result, I have been using transparent lure box. The advantage is that each box has a dozen separated compartments. It saves a considerable amount of time that you have access to a dozen (or more) larvae with the flip of a lid. The time that it took to feed one larva, I can now feed a dozen or more. This technique is no longer cost efficient for the larger L3 larvae due to the higher cost of the lure box.
Getting Ready for Pupation: Raising your larvae to maximum size is the easy part of Goliathus breeding. The majority of failures are caused by the larva’s inability to successfully build its pupal cell. Special attention from the breeder is required to able to read the first sign of readiness to pupate.
- The larva will stop eating. Look for uneaten and moldy food.
- The larva will gain a slight yellowish taint, not as pronounced as Dynastidae larvae however. Pay attention to its color.
- The larva will be in constant movement (I often use the analogy of a devil in Holy water) and will try to escape its container at all cost. You can compare this behavior to a more docile larva which is still in development. Keep all your larva containers in a larger plastic box and allow them to “escape” its individual container. The larva should be able to lift the lid by itself. When you encounter a larva that is roaming inside the larger box, it’s probably looking to pupate. They move so much that I sometime cannot have a proper weight reading.
- The larva will be extremely aggressive and will try to bite you when held. Hold the larva with your fingers and it will “snap” back in a C-shape in the hope of biting you.
- The larva will lose up to 10% of its weight. A digital weight scale is a good tool to monitor its development. As soon as the larva starts losing weight, you can put it under observation. However you must weight your larva on a regular basis and keep a weight chart for comparison.
- The larva will start crawling on its back on the surface for several weeks, a behavior called the “Wandering Phase.” If kept in a small container; the substrate will be completely compacted due to the constant movement of the larva. If not transferred rapidly at this point, the larva may die from exhaustion.
- The larva’s body will lose some of its firmness. With experience you will be able to recognize the firmness of a larva in development and one that is ready to pupate. I believe that all the signs listed above (when combined) should allow a breeder to properly read the behavior that a larva is ready to pupate.
Note: There is nothing more frustrating than to lose a larva just before it’s ready to pupate (such as section #6 above). That is countless of hours wasted! However, if you encounter a larva that is completely flaccid, it may or may not be dead yet. You should burry the larva in fresh substrate and wait 24 hours. It is my experience that if the stress level was not lethal, the larva will slowly reanimate and regain its firmness within the hours. If it is too late, your dead larva will start smelling. I have discovered this behavior after finding a healthy larva in my waste basket that I thought was dead.
Once you have a larva that is ready to pupate, you must transfer it to another container that is only used for pupation. I have experimented with many container sizes (starting with a single larva in a 30 L. bucket at the beginning) and I have narrowed it down to a plastic shoe box which is the most economic in terms of space. As pointed out earlier, a wandering larva will be in constant movement and a dire need to escape whatever container it is placed in. A pair of heavy duty rubber band is recommended to hold the lid in place and prevent the larva from lifting the lid and escape. The wandering will last between 2 to 4 weeks and a trench following the circumference of the container will be made on the surface where the larva crawled through. Once its need to wander is satisfied, it will then disappear under the substrate and form its cocoon. To keep track of the duration of that phase, I would “reset” the trench made by the larva with my hand and keep track of the current date. The dates would give me an idea of when the larva was on the surface last. For example, if you “reset” the substrate and the surface is intact after 4 weeks then there is a good chance that the larva has undergone its cell construction. Once the cocoon is built, any handling should be made with extreme care. I have had a bad experience when I dropped a container too hard on a table and the shock would disturb the larva to the point where it would break and leave the cocoon. Of course, the larva would not build another cell and eventually die. In contrast to some Cetonidae species, Goliathus larvae will never create a cell which shares a side with the wall of the container.
The substrate composition that I use for pupation is 20% peat moss and 80% coarse sand. The coarseness of the sand will dictate the sturdiness of the cocoon. When fine sand was used, the cocoon was much more fragile than when built with a coarser one. This mix of peat moss and sand should be filled to the rim of the pupation container. The great majority of the cells will be created near the bottom of your container. After 4 weeks on inactivity where no further sign of wandering is seen, you can take out pupa cell if needed (for example, needing the pupation container for another larva). This can be done by very gently scooping out the substrate until your fingers feel a hard crust. This will be the pupa cell. Once the cocoon is located, you can work around the cell until it is free from the substrate. Place the cell facing the same orientation as originally found in another container which will hold all your pupal cells until their emergence. This holding container should have a layer of the sand-peat moss mix at the bottom. An important thing is to cover each cocoon with some of its original substrate. This will allow a gradual dehydration of the cocoon starting from its original moisture level. The holding container should never be allowed to completely dry up. Adding moist substrate from newly added cells may be enough to keep the container moist until it is full; at which point, slight misting may be required. The ideal situation would be to allow the pupa to complete its metamorphosis in its original pupation container as this will create the least amount of stress to the cell. This may not be a possibility when you have a large population of larvae.
Humidity level: The humidity level necessitates a paragraph of its own as it is the number one cause of failure experienced by Goliathus breeders (including myself). A substrate which is too dry will discourage the larva from building its cocoon. The opposite is no good either as the larva/pupa may die inside its cocoon. The proper substrate humidity is achieved when substrate particles stain your fingers when rubbed together but not damp enough to make clumps and stick together. As a general rule, you are safer on the drier side than on the damper side. No one knows for sure the reason why the Goliathus pupa is so sensitive to the moisture level. One hypothesis is that the pupa expects the same condition encountered in the wilderness. The adults emerge and lay their eggs during the rainy season and the larvae continue their development until the dry season arrives. At which point, the larvae create their cocoons. As the ambient moisture dissipates, the cocoon hardens gradually and remains dormant until the next rainy season arrives and the cycle continues. At the next rainy season, the imago is stimulated to emerge with the return of a higher humidity. Once the larva has become a pupa, it will take about 3-4 months to become an imago. The imago will lie dormant for another 3-4 months in its pupal cell before it becomes active. When you come near the final few months, you can stimulate the beetle to emerge from its dormancy by placing the cell back to a larva substrate (80% leaf, 20% wood) with a moisture level appropriate for larva care. You can help the beetle a little bit by removing a section of the cell facing the head of the beetle. However, if you do so, you must burry the cell with the beetle at the bottom of your tank. An imago that is not 100% active yet may crawl out of its cell and flip over and die from exhaustion. The female imagos are usually the first to emerge due to their smaller sizes. Once the beetle is capable of locomotion and can eat by itself then you can have successfully completed your cycle.
Similarity (and difference) between the species: My personal experience has been with 4 different species of Goliathus: Goliathus goliatus, Goliatus orientalis, Goliathus regius and Goliathus cacicus. The first 3 species are pretty much kept the same way as described in this article. However for some unknown reason, my Goliathus orientalis did not live very long and the males never emerged from their dormancy. Goliathus cacicus, still remains a mystery. Although kept in the same condition as the other species, I have never achieved the same growth as for my other species. The maximum size for a male larva was about 40g. That is the size of a Mecynorrhina male. A large Goliathus cacicus male can attain 10 cm. Something is missing in the diet or rearing condition and further experiments will be required. As for Goliathus albosignatus, I have communicated with some breeders who have it in their breeding. Due to their smaller sizes (maximum larval weight of 30g.), it takes about half the time to complete the cycle (L1-start of pupation: 3-4 moths; pupation: 4-5 months; dormancy: 1-2 months). The rearing requirement is similar to Goliathus goliatus.
In conclusion, I consider myself extremely lucky to have had the opportunity to rear these incredible creatures from egg to imago form. Very few people have had the chance to see these beetles live, let alone handle them. Whether I continue my Goliathus breeding or not (due to the lack of time), I sincerely hope other breeders can find this article helpful. Little is known about the ecology of the Goliathus and the information we know about them was found because of a handful of dedicated breeders. As incredibly rewarding as it may be, I would not recommend the breeding of Goliathus to a novice. Other smaller species such as Mecynorrhina or Chelorrhina have similar but simpler requirements.