Complete Guide to Raising Mandibularis Stag Beetles | How to Keep the Tropical Stag Beetle with the World's Longest Mandibles | ブリちょく
Insects| ✍️ BreederDirect Editorial
Complete Guide to Raising Mandibularis Stag Beetles | How to Keep the Tropical Stag Beetle with the World's Longest Mandibles
Mandibularis stag beetles are among the world's largest stag beetles, native to Borneo. Their distinctive feature is enormous mandibles that can exceed body length. This guide details all breeding steps from larval management, temperature control, egg-laying setup, pupation, and emergence.
Key Takeaways
Mandibularis stag beetles are among the world's largest stag beetles, native to Borneo. Their distinctive feature is enormous mandibles that can exceed body length. This guide details all breeding steps from larval management, temperature control, egg-laying setup, pupation, and emergence.
The Mandibularis stag beetle (Hexarthrius mandibularis) is one of the world's largest stag beetles, found primarily on Borneo and Sumatra. In large specimens, the mandibles can develop to nearly exceed the body length, and their magnificent appearance captivates stag beetle collectors worldwide.
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Adults require large enclosures (approximately 60 cm × 30 cm) with fruit fly prevention. Use fermented substrate, 3–5 cm deep. Always include bark or driftwood for climbing and to prevent overturning, as large beetles cannot right themselves and will weaken if flipped.
Temperature: 22–26°C (high summer heat is detrimental)
Humidity: 50–70% (avoid excessive dryness)
Climbing wood and turnover prevention materials: Multiple large pieces recommended
Feeding
Feed high-protein, high-sugar insect jelly. Mandibularis beetles consume more jelly than other stag beetles.
Replacement frequency: Every 2–3 days (remove uneaten portions)
Multiple beetles: Males are territorial and mandibles can break during fights, so individual housing is strongly recommended
Breeding (Egg-Laying Setup)
Pairing
Pairing must always be done under supervision using hand-pairing. Leaving them together unsupervised is not recommended due to frequent accidents where males crush females during mating.
Hand-pairing procedure:
1. Feed both beetles well beforehand to ensure adequate stamina
2. Place the female near the male, and if he responds, assist him in mounting
3. After confirming mating (5–15 minutes), separate immediately
4. Repeat a few days later to improve fertilization rates
Egg-Laying Setup
Using mature breeding wood (rotted logs or chinquapin) is most effective for egg-laying.
How to prepare the egg-laying setup:
1. Breeding wood: Soak chinquapin or oak breeding wood in water for 12–24 hours, then air-dry in a shaded area to achieve proper moisture
2. Substrate: Place fine-grain or fermented substrate 5–7 cm deep on the bottom
3. Wood placement: Embed the breeding wood halfway into the substrate
4. Temperature: Maintain at 24–26°C
5. Introduce female: Egg-laying begins within 2–3 weeks, lasting approximately 1–2 months
After egg-laying, you will notice small holes (egg marks) on the wood surface or softened areas. Check for eggs 2–3 months after laying before excavating.
Larval Management
Larval Excavation
Carefully split the breeding wood and remove larvae without injury. Mandibularis larvae are relatively large (5–10 mm even at first instar) and easy to identify.
Instar size guide:
- 1st instar: 5–10 mm
- 2nd instar: 15–25 mm
- 3rd instar: 40–60 mm
Larval Rearing Method
Mandibularis larvae are best reared in fungal substrate bottles, which produce the largest adults.
Instar
Recommended Container
Recommended Fungus
1st
200–500 ml cup
King trumpet mushroom strain
2nd
800–1100 ml bottle
King trumpet mushroom strain
3rd
1400–2000 ml bottle
King trumpet or oyster mushroom
Replace substrate when it deteriorates, turns brown, or the larva reaches the sides. Some breeders switch to fermented substrate during late 3rd instar.
Temperature management: Optimal temperature is 22–24°C. Above 24°C, the larval period shortens and adults remain smaller.
Pupation and Emergence
When mature larvae begin pupating, they create a "pupation cell." Once this sign appears, do not move the bottle.
Signs of pupation:
- Stops feeding and body shrinks (pre-pupae stage)
- Larva color turns yellowish
- Pupation cell formed at sides or bottom of bottle
Pupation lasts 2–3 months. After emergence, allow 1–2 months for the exoskeleton to harden before the beetle begins eating. Once feeding resumes, the beetle can be used for breeding.
Tips for Raising Large Specimens
Use larger fungal bottles: Using 2000 ml bottles for 3rd instar directly increases size
Avoid frequent disturbance: Stress causes aggressive feeding and overgrowth
Use high-quality breeding wood: Good-quality mature logs are key to producing large larvae
Precautions and Legal Considerations
Keeping and selling Mandibularis stag beetles is legal in Japan, but releasing them into the wild is absolutely prohibited due to ecological concerns. When disposing, seal them in a bag before discarding.
When purchasing imported specimens, verify with your supplier that they are not regulated under CITES (Convention on International Trade in Endangered Species) and that they come through legitimate import channels.
Conclusion
The Mandibularis stag beetle is popular among intermediate breeders for its impressive mandibles and striking appearance. By combining proper temperature management with fungal substrate rearing, you can successfully raise specimens exceeding 100 mm. Beyond size, the satisfaction of successful breeding and larval management is the true reward of stag beetle keeping.
