
Source: Wikimedia Commons
Phalacrognathus muelleri
The world's most beautiful stag beetle from Australia. Iridescent metallic rainbow body is its defining trait. Docile and easy to keep. Larvae thrive on both fungus bottles and substrate.
Phalacrognathus muelleri, the rainbow stag beetle, is the sole species in its genus and belongs to the family Lucanidae. Native to the rainforests of northern Queensland, Australia, and New Guinea, it is celebrated for its remarkable iridescent coloration, appearing in red, green, blue, or black forms depending on the individual. Adults reach 30–65 mm in length and inhabit tropical forest canopies, feeding on tree sap and fruit. In captivity, small to medium enclosures are suitable, furnished with pieces of bark and wood to prevent toppling. Egg-laying occurs directly in fine-particle fermented substrate packed to a depth of at least 10 cm. Optimal temperature is 20–25°C, and adults live one to two years—an unusually long lifespan for stag beetles. Its spectacular coloration, manageable size, and straightforward husbandry make it one of the most sought-after display beetles worldwide.
Source: Wikipedia (CC BY-SA 4.0)
Origin
northern Queensland, Australia and New Guinea
Lifespan
Adult 1-2 years / Larva ~8 months
Size
30-70mm
Temperature
20〜26℃
Humidity
60〜80%
Jelly (adult) / Fungus bottle or fermented substrate (larva)
Captive record (♂)
70.1 mm
Wild record (♂)
70 mm
Record source: BE-KUWA 2025年度版(ニジイロ 飼育70.1mm 飯島和彦 2023 / 野外70.0mm)
Notable localities
金属光沢の虹色が特徴。飼育が容易で人気。飼育レコードは BE-KUWA(むし社)のコンテストで毎年更新される。産地・累代(CBF/WF/WD)・サイズで個体価値が大きく変動する。
Generation codes
Sources: BE-KUWA 認定飼育レコード(むし社、2025年度版)
Edited & verified by: br-choku editorial team
The taxonomic, regulatory, and husbandry data on this page are compiled and verified against the authoritative primary sources below.
Accepted name: Phalacrognathus muelleri (MacLeay, 1885)
Synonyms: Lamprima muelleri MacLeay, 1885, Phalacrognathus muelleri fuscomicans Kolbe, 1908, Phalacrognathus westwoodi Shipp, 1893
Authority databases: GBIF
Nomenclature follows global taxonomic authority databases.
Plant Protection Act: コガネムシ上科(カブトムシ・クワガタムシ・ハナムグリ等)の生きた個体を輸入する際は、外来生物法に基づき輸出国政府機関等が発行する種類名証明書の添付が必要(輸入港は成田・中部・関西・福岡・鹿児島の各空港に限定)。本種自体は特定外来生物ではなく、証明書の添付により輸入可能。
Sources: 環境省 外来生物法「コガネムシ上科に含まれる生きた昆虫を輸入される方へ」 / CITES 附属書(checklist.cites.org)
Regulations may change. Always verify the latest information with the relevant authorities.
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Small-medium case. Add plenty of bark to prevent flipping
Lays in substrate. Pack fine fermented mat deeply
Both fungus bottles and substrate work. Temperature is key to size
Adults take 2-3 months before starting to feed after eclosion
Beginner. This is a beginner-friendly species. No special equipment or experience is required, and it can be kept successfully with basic care setup.
The ideal temperature for Rainbow Stag Beetle is 20〜26℃. Recommended humidity is 60〜80%. Avoid sudden temperature changes and maintain a stable environment.
The average lifespan of Rainbow Stag Beetle is Adult 1-2 years / Larva ~8 months. With proper care and nutrition, they can live a long and healthy life.
Rainbow Stag Beetle typically reaches 30-70mm as an adult. Size may vary depending on care conditions and individual genetics.
Rainbow Stag Beetle feeds on: Jelly (adult) / Fungus bottle or fermented substrate (larva). Aim for a balanced diet with appropriate feeding frequency.
The price of Rainbow Stag Beetle varies significantly depending on morph, size, and lineage. Check our market price page for the latest pricing information.
Last updated: June 23, 2026