Beginner's guide on rearing beetle larvae

In this page, I'll try to cover the basics of rearing beetle larvae. 

If you are a novice in rearing beetle larvae, I hope reading this answers most of your questions!

 

1. Understanding beetle larvae

1. Larval instars. Stag beetles, rhinoceros beetles, and flower beetles progress through a series of developmental stages, from eggs to emerging adults. These stages include first-instar larvae (L1), second-instar larvae (L2), third-instar larvae (L3), and pupa. With each molt, the larva advances one instar. The first and second instar stages are relatively short, while the third-instar stage takes the longest.

2. Larval periods. The duration of the larval period varies across beetle species. For instance, smaller stag beetle species like Lamprima adolphinae complete their larval period within 4-6 months, while larger rhinoceros beetle species such as Megasoma elephas require 18-24 months to complete their larval period.

The duration of the larval period can be influenced by a range of external factors such as temperature. Generally, low temperatures prolong the larval period, whereas high temperatures accelerate it.

3. Pre-pupal stage. Upon reaching the stage when L3 larvae are prepared to construct pupal chambers, they undergo a noticeable transformation. Their skin becomes wrinkled, and their coloration shifts to yellow. Typically, these larvae create their pupal chambers at the bottom of the container, making them easily observable. A sturdy pupal chamber is essential for a successful pupation. If the pupal chamber is accidentally damaged or destroyed, a substitute chamber must be constructed, as larvae at this stage lack the capacity to construct a new one.

Pre-pupa larva in their pupal chamber.

Pre-pupa larva in an artificial pupal chamber.

5. Pupa stage. During this period, the color of the pupa will continue to change. When the head, thorax, legs, and elytra darken, it's a sign that the pupa will soon emerge to become an adult beetle. Given their delicate nature, handling of newly emerged beetles is not recommended.

6. Dormant stage. Following emergence, beetles undergo a period of dormancy in which their exoskeleton and internal organs mature to suit their new life stage. During this phase, adult beetles neither feed nor move, and handling should be kept to a minimum due to their fragility and susceptibility. The duration of the dormancy period depends on the species. High temperatures usually shortens the dormancy period.

 

2. Larva food

1. Understanding flake soil. In the natural world, many rhinoceros, stag, and flower beetle larvae feed on white-rotten hardwood. Conversely, beetle hobbyists often feed their larvae fermented sawdust, commonly referred to as flake soil. Flake soil is preferred by hobbyists due to its high nutritional value, safety, and stability in comparison to white-rotten hardwood.

2. Flake soil humidity. Prior to feeding larvae with flake soil, it is necessary to ensure that the soil's humidity level matches the larvae's requirements. A typical approach to verifying the ideal moisture content is to grasp a handful of flake soil and compress it. If the soil forms a cohesive clump without any moisture seeping from one's hand, then the moisture content is appropriate. However, the specific moisture requirements may vary somewhat among different species and can have the flake soil slightly wetter or drier than the standard.

Here is a video of a Japanese breeder adjusting the humidity of his flake soil:

One minute and thirty seconds into the video, the ideal humidity is shown. 

3. Aerating flake soil. Flake soil that has been stored in air tight bags must be aerated for several days before use, as it may generate harmful gases and heat. Aerating allows beneficial bacterial and fungal colonies to stabilize the flake soil, which creates a hospitable environment for the larva. If this step is skipped, the larvae could potentially suffocate and die; therefore, you should never skip this step. 

3.1 Step by step guide on how to aerate flake soil:

1. Pour the flake soil into a container

2. Add water to the flake soil if it's below the standard humidity

3. Put a cloth or breathable covering over the container to prevent fungus gnats from entering

4. Let the flake soil sit inside the container for a day or two

5. Check if the flake soil is generating heat or smells of ammonia. 

6. If the flake soil is generating heat or smells of ammonia, mix the flake soil around and wait a couple more days.

7. Once the flake soil is stabilized, you can use it to feed your larvae.

4. Replacing flake soil/substrate. Beetle larvae need to have their flake soil replaced once 2/3 of the flake soil have turned into feces. When replacing flake soil, do not throw away the old flake soil completely. Keep a little bit of the old flake soil and mix it with the new flake soil so that the larva can quickly adapt to the new soil. This step is important, especially if you are purchasing flake soil from different sources because the raw materials and nutrients (including ratios) used can be different. 

         

Flower beetle larva container full of feces. Overdue for replacement. 

 

3. Larvae rearing container

1. Selection by instar. The size of the container required for beetle larvae depends on the larval stage and the species. First-instar(L1) larvae are small so they can be individually kept in 2-6oz containers. From the second-instar stage onwards, larvae can be kept in 16-32oz containers. Larger species such as Megasoma elephas require at least 4L containers from the third-instar stage onwards, as they can grow to massive sizes.

2. Selection by species. As mentioned above, Megasoma elephas larvae can get really big, so it's no surprise that they require big containers. General guidelines and container size requirements are listed for each species on my "Care sheets" page, so make sure you check out the guide for your species. 

 

 4. Temperature

1. Ideal temperature. Due to their different ecological origins, each species can adapt to slightly different temperatures. Tropical species usually require warmer temperatures(73-80°F), while temperate species prefer cool temperatures(64-70°F). Generally, most beetle species are able to develop optimally at room temperature, which typically ranges between 70-77°F.

2. Adjusting temperature. The matter of temperature regulation in beetle rearing can be complex as it is subject to personal preferences and budgets, and there are numerous methods available for adjusting temperature.

The majority of hobbyists tend to use air conditioners to either cool down or heat up their rearing spaces. However, some may opt for more specialized equipment such as wine coolers or temperature-controlled shelf cabinets to maintain the ideal temperature for their larvae. Ultimately, the choice of equipment and approach will depend on individual financial resources and creative solutions.

 

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This page covers the basics of rearing beetle larvae. While this much information may appear overwhelming to beginners, a comprehensive understanding of these principles will simplify the process of rearing beetle larvae.

If you still have any questions about rearing larvae or beetle keeping in general, do not hesitate to contact me.

Thank you for taking your time to read it through! If there are any mistakes, I will be sure to correct it.