The Goliathus goliatus is undoubtedly one of the best-known and most popular beetle species, highly regarded among both collectors and breeders.

This guide is intended for those who wish to observe the species' development from egg to adult under home conditions. It is important to emphasize that G. goliatus is one of the most specialized beetle species in terms of care requirements, demanding careful attention, precise conditions, and consistent rearing practices. It is generally not recommended for beginners; however, with proper dedication and research, successful maintenance is possible even without prior experience.

The method described here is a personal rearing technique developed over many years, which we still apply successfully today. Based on our experience, this approach provides stable and reproducible results.

1. Larvae rearing
2. Pupation
3. Active imago care
4. Breeding

1. Larva rearing

The rearing of Goliathus goliatus larvae, although one of the more complex parts of keeping this species, does not represent the greatest challenge in their care.

The larvae are particularly robust, tolerate changes well, and generally adapt well to their environment. Nevertheless, it is important to emphasize that the foundation of successful rearing is regular, controlled, and cyclical care. The absence of this – even to a small extent – almost always negatively affects the growth rate and the size of the imagos. Inadequate attention often results in smaller, weaker individuals, which in the long term diminishes the success and sustainability of breeding.

Therefore, consistent observation, stage-specific interventions, and strict adherence to rearing parameters are indispensable for the effective care of the species.

The ideal temperature for the larvae is between 18–26 °C, with stable, fluctuation-free conditions being a primary concern. Their placement should preferably be in a dark, sunlight-free location.

The proper humidity ranges between 50–70%. Since rearing usually takes place in smaller, closed containers, humidity can be well regulated by increasing or decreasing ventilation, or by adjusting the amount of water added to the substrate. Excess moisture must be avoided, as it can lead to anaerobic conditions, which hinder development.

Larvae must be kept individually, separated from each other, as they are prone to cannibalism, which can cause significant losses in communal rearing.

It is very important to emphasize that larvae consume a general soil intended for flower beetles only for a short time after hatching from the egg. Once they strengthen, their main diet becomes high-protein materials. This dietary characteristic makes them special and explains their rapid growth and the relatively short time in which they reach the weight necessary for pupation.

Here the importance of cyclical care returns. Once feeding with protein-rich food begins, it is advisable to replace the soil with peat that has a pH value of around 7, which is a cost-effective solution for keeping the substrate clean. It is important to note that larvae no longer consume the soil, but protein cannot remain edible for long in their container, so fresh feeding every 3 days is necessary.

Each individual's container should be clearly labeled to track their development. During feeding, it is useful to keep a simple chart recording how much food the individual consumed during the previous feeding.

Uneaten food must be removed and replaced with fresh food during every feeding. It is important to carefully monitor the protein intake of each individual; to facilitate this, pellet-form food is recommended, as it can be easily dosed and tracked by piece count. Before feeding, pellets should be soaked in water: softened pellets are easier for the larva to consume and partly satisfy their water needs due to moisture content. Food should be placed in a small pile on the surface of the substrate. If the previous portion is completely eaten, the next portion can be increased; if a significant part is left uneaten, the portion should be reduced. It is important to keep the larva in a container of appropriate size: if the space is too large, it may have difficulty finding the food, which can slow growth.

Protein-rich food typically begins to mold after three days, which is normal. Due to the structure of the peat substrate, moldy pellets often clump together, making them easy to remove as a whole. Since the amount of substrate may gradually decrease during cleaning, it is advisable to replenish it every time so that larvae can continue developing in sufficient medium.

This method ensures that individuals capable of significant growth receive the necessary amount of nutrients and develop optimally.

When selecting protein-based feed, it is worth experimenting with several formulas. Products with more than 30% protein content may also be suitable, provided their other parameters do not significantly deviate from the optimal. Regarding fat content, 5–15% is considered ideal for the larvae. Higher-fat foods – such as dried silkworm pupae – are recommended more as supplements rather than primary food.

The size of the storage container for larvae varies according to developmental stage. For L1 larvae, a 150–280 ml container is sufficient, for L2 at least 500 ml is necessary, while L3 individuals should be provided with 1–2 liter containers. Flat plastic boxes that can be hermetically sealed are ideal.

However, every container must have appropriately sized ventilation holes covered with microporous tape. This solution ensures air exchange while preventing pest entry. Covering the ventilation holes significantly reduces the risk of mite infestation and other infections, thus eliminating the need for thorough inspection or intervention at every feeding.

Containers do not need to be filled completely with substrate. Since larvae no longer feed on the substrate at this stage, its primary role is to maintain proper humidity. Therefore, it is sufficient to place enough substrate in the container to cover the larva completely in every position. This provides a comfortable environment without unnecessary excess medium.

The larval stage usually lasts 5–7 months and is influenced by many factors, mainly temperature. Higher temperatures speed development but often result in smaller body size. Moderate temperatures of about 22 °C slow development but allow larvae to reach larger mass before pupation.

By the end of this period, females typically reach 30–50 g, and males 50–90 g. The 3-day feeding cycle must be followed consistently throughout the entire larval stage, i.e., at least half a year. This process requires significant attention and represents one of the greatest challenges of rearing.

Although their development is relatively fast compared to other species of similar size, many problems may arise during the 6-month larval stage that can lead to mortality. One of the most common is the proliferation of mites in the larva's container on mainly protein-rich food. A small number of mites usually causes no serious problem, but explosive growth disturbs the larva and can impede development.

If mite presence is significant, a simple bathing procedure can restore hygienic conditions. This is why it is especially important to cover the container ventilation holes with microporous tape, as mites easily spread between containers, causing severe problems throughout the breeding stock.

During the 3-day cyclical care, the animals must be checked at every feeding, and interventions performed as necessary. This preventive approach keeps mites and other unwanted parasites under control, allowing the larva to safely reach its developmental potential.

Mention should also be made of another type of mite often encountered by beginner beetle keepers, which differs from the freely visible, moving mites. In this case, a yellowish or pinkish, dust-like deposit appears on the larva's body surface. These are also mites but they live directly on the larva's body, using it as their habitat.

Their removal is much more difficult than that of the moving mites, as they adhere strongly to the larva's surface, so a simple bathing method is insufficient for treatment. To effectively eliminate them, one must first understand their cause: experience shows that these mites survive only under high humidity. The problem usually arises from too much water in the substrate without adequate ventilation.

In both mite cases, substrate replacement is crucial. Ideally, the larva should be transferred to a clean container filled with fresh substrate, minimizing mite recolonization and ensuring undisturbed development.

The best defense against dust-like mites is reducing humidity to a level still suitable for the larva but unsuitable for the mites.

After reaching the ideal weight, larvae enter a so-called wandering phase. During this period, they move on the substrate surface, stop feeding, and intensely try to leave the container. This is because the previously used peat-based substrate is entirely unsuitable for pupation, so the larva instinctively tries to find a suitable environment to build its pupal chamber.

During this phase, using a properly sealable container becomes especially important. Larvae are very strong and mobile at this stage, with excellent climbing ability compared to other species, so the risk of escape is high. A single escaped individual can quickly move a considerable distance.

The wandering phase lasts until the larva finds a suitable medium or accepts the given conditions. If this does not happen, it may die on the surface or unsuccessfully attempt to pupate in the unsuitable substrate. The chance of survival in the latter case is minimal. Safe pupation is only guaranteed if the larva is transferred on time to a suitable substrate with appropriate quality and structure.

The species requires a special medium for pupation, consisting of a clay and sand mixture. This material is essential for constructing a stable and sufficiently solid pupal chamber. It is also very important that the substrate is drier than one might initially think.

Males over 60 grams should be placed in containers of at least 5 liters, while smaller individuals – regardless of sex – can be kept in 2.5–3 liter containers. The storage containers should be completely filled with the appropriately composed medium.

At this stage, it is advisable to weigh the larva and carefully remove all mites. Ideally, these steps have already been done before the wandering phase started, so no further intervention is needed now. However, if unavoidable, it is crucial that the larva is transferred mite-free and clean into the pupation medium, as this is a prerequisite for successful and trouble-free pupation. The larva is simply placed on the substrate surface; it may take a few days before it burrows in and begins building the pupal chamber.

2. Pupation

The onset of pupation marks the most critical period in the larva's life cycle. Unfortunately, most mortality occurs during this relatively long phase. The Goliathus goliatus larva builds an extremely strong, massive pupal chamber, which it characteristically reinforces in the middle. One of the species' unique traits is that—unlike many other flower beetles—the transformation inside the constructed pupal chamber does not begin immediately; the larva can remain in an unchanged state for months. This long waiting period presents many challenges for breeders and requires particular care in maintaining stable conditions.

Most errors during this stage result from moving the box containing the pupal chamber prematurely and without reason. This can cause significant stress to the larva, often leading it to break out of its own chamber and perish outside.

Therefore, after placing the larva that is in the wandering phase into the appropriate pupation medium, a quiet, dark location must be found where it can rest undisturbed for at least 4–6 months. It is important that the box is not subjected to any shaking or movement during this time, as this can directly endanger development.

About 5 months after the start of pupation, the egg-shaped pupal chamber can be carefully removed from the original box and moved to a smaller, well-observable location. Based on our experience, it is advisable to position the pupal chamber according to its original orientation; therefore, it is important to note which side was facing up. This can be marked with a simple note, which should also indicate the exact start date of the wandering phase.

The pupal stage lasts approximately 2 months, but the exact time may depend on the beetle's size—smaller individuals develop faster, larger ones slower. If necessary, the developmental state can be checked very carefully through a small opening at the top of the pupal chamber. This must always be done with extreme caution and without damaging the structure of the chamber.

If the pupa successfully transforms into an adult, it typically undergoes an inactive period of 2–4 months, spent as a fully developed beetle but still inside the pupal chamber. When the time comes and the animal is ready to feed and mate, it breaks out of the cradle and vigorously tries to exit the storage box.

It is important to emphasize again that the active Goliathus goliatus possesses extraordinary physical strength. It can easily bend softer plastics, so it is not worth skimping on the quality when selecting the storage container. Losing an individual cared for over many months—or even having it escape inside the home—can be a significant loss; therefore, it is especially important to keep the adult in a secure, sturdy box.

3. Active imago care

For housing freshly emerged, active adults, substrates such as wood shavings, peat, sphagnum moss, or any well-maintainable medium with appropriate moisture retention can be used. The most suitable food is jelly specifically made for beetles, which should be replaced weekly; for females, it is advisable to use a protein-enriched variant. Alternatively, fresh, juicy fruits (e.g., banana, mango, peach, melon) can also be offered, but from a breeding perspective, beetle jelly is preferable because it requires less frequent replacement and its higher energy content positively influences males' mating performance and females' egg production.

Excessive moistening of the substrate is not necessary; if the adult feeds regularly, this alone is sufficient to prevent dehydration. It is strongly recommended to keep the animals individually isolated, as this reduces energy loss and results in calmer behavior. If an active male and female are placed together in the same container, the male often immediately attempts to mate. In long-term cohabitation, too frequent and unnecessary mating attempts quickly exhaust both individuals, significantly reducing their lifespan.

Do not forget to provide an appropriately sized and stable climbing surface on top of the substrate, which offers enough grip for the animals. This is especially important during movement and feeding, and helps if they accidentally flip onto their backs.

Do not be surprised if a solitary male, after consuming the available food, continuously tries to escape. This likely does not indicate unsuitable conditions. It should not be forgotten that these animals instinctively focus solely on mating after becoming fully developed beetles. In fact, their main life goal is to mate as many times as possible.

4. Breeding

Successfully reaching the breeding stage is already a significant achievement. Goliathus goliatus reproduction requires only one fresh, active pair. Before starting breeding, it is advisable to feed the female with protein-rich jelly for two weeks, while the male should be fed standard, carbohydrate-rich beetle jelly to ensure sufficient energy for mating.

It is recommended to set up a so-called "pre-breeding" box, which serves specifically to observe whether mating has occurred. This method has proven effective with other species as well. Prepare a 10–15 liter plastic container with only a minimal amount of soil and provide climbing surfaces. Essentially, double the minimum living space required for adult beetles to accommodate a pair comfortably. The beetles are confined together in this box for one week. Provide only one feeding site in the box to encourage encounters: in nature, it is common for fertilization to occur while the female is feeding.

During the one-week cohabitation period, prepare the appropriate breeding box for the female, where she can begin laying eggs. The box volume should be at least 20 liters, but ideally choose a 45-liter plastic container. It is essential that the box can be closed securely to prevent escapes and to keep out external disturbances.

The box height should be at least 25 cm, with about 20 cm filled with substrate. Use fine-structured soil suitable for breeding flower beetles. Firmly compact the bottom layer (about 10 cm deep). Fill the upper layers with soil as well, but only lightly press down so the female can easily dig.

It is recommended to place dry leaf litter on the soil surface, providing a more natural environment and helping maintain the proper microclimate. The leaves can be lightly misted with water to prevent excessive drying but should not be too wet. Lower soil layers can be slightly moister, while upper layers remain drier.

Do not forget to place appropriate climbing surfaces as well—these are essential for the adult beetles' comfortable movement.

The breeding box should be checked weekly. At these times, replace the gel or fresh fruit offered to the female to ensure constant access to adequate nutrition. However, the entire substrate should only be turned over after about 2–3 months—by then, eggs or freshly hatched small larvae will likely be found.

It is important to know that females' egg production varies greatly between individuals: sometimes they lay only 5–10 eggs, but more than 50 offspring can hatch from a single female. Therefore, it is crucial to be prepared in advance to provide proper placement and care for the fresh larvae if breeding is successful—this ensures the entire cycle can continue smoothly.