Rainbow Stag Beetle Fact File

Phalacrognathus muelleri 

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Wild 18 months

Captive 18 months



Fruit, Decaying Wood

Conservation Status


Not Evaluated

The rainbow stag beetle is named for the bright coloration found on the elytra (wing covers) which sit on the abdomen of these animals.

Much of their life is spent as a juvenile known as a larvae. All of their growth occurs during this time. Once they complete their pupation the adult beetle does not grow any larger.

Both adults and larvae will feed on decaying wood. In captivity they can be fed fruit.

They are kept as pets both in their native Australia and overseas with one of the most popular locations being in Japan.

Read on to learn more about these incredible invertebrates.


What does the rainbow stag beetle look like?

The rainbow stag beetle is brightly colored with a metallic looking back which is colored with greens, blues and reds. Their mandible and legs are colored black. They have six legs.

Young are a larva with a segmented body which is white and has a facial patch which is orange.

Males are larger than females. The male measures between 24 and 70mm (0.9-2.8in) while female’s measure 23 to 46mm (0.9 to 1.8in).

A range of factors during the development of the larvae lead to the large variation in size. The larger beetles have larger mandibles making them better at fending off other males.


What does the rainbow stag beetle eat?

The rainbow stag beetle is a herbivore. They feed upon decaying wood as both adults and larvae. As adults they supplement their diet with fruit, sap and nectar.


Where can you find the rainbow stag beetle?

Australia is the native home of the rainbow stag beetle. Here they are found in north-eastern Queensland.


What kind of environment does the rainbow stag beetle live in?

They are found in rainforests and sclerophyll forests.

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How does the rainbow stag beetle produce its young?

This species can breed throughout the year. A female stag beetle is capable of laying up to 50 eggs which are laid singly. These are laid into rotting wood and hatch after 10 to 14 days. Across this period the egg doubles from the original size and the larvae becomes visible.

The rainbow stag beetle spends 2 months as a larva feeding upon the wood in which they were born. They molt three times as a larva before becoming an adult by pupating.

The pupation takes place in a pupal cell which they build over a week. The pupa spends their time developing before emerging by breaking out of the pupal cell using their mandibles. When they emerge their wings are soft and white which take a week to color up.

From day one they are independent.

It takes four months for the adult to be sexually mature.


What does the rainbow stag beetle do with its day?

This species is able to fly and it is when they do this that they are most often spotted.

Rainbow stag beetle

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Predators and Threats

What is impacting the survival of the rainbow stag beetle?

Birds are a natural predator of the rainbow stag beetle.

The rainbow stag beetle is a popular pet both in their native, Australia and overseas especially in Japan. Some may be captured from the wild to supply this trade but they are also bred in captivity.

Quick facts

The mulleri portion of the scientific name was given to this species by Sir William Macleay who discovered it in honour of Baron Ferdinand von muller who was a botanist with the Victorian government.

Rainbow stag beetles are also known as the magnificent, Mueller’s or king stag beetle.


Henderson, A., Henderson, D. and Sinclair, J., 2012. Bugs Alive. Melbourne: Museum Victoria.

Wilbur's Wildlife. 2020. Rainbow Stag Beetle. [online] Available at: <https://wilburswildlife.com.au/our-animals/rainbow-stag-beetle/> [Accessed 24 April 2020].

Shop.minibeastwildlife.com.au. 2020. Care Guide Rainbow Stag Beetle (Phalacrognathus Muelleri). [online] Available at: <https://shop.minibeastwildlife.com.au/content/Minibeast%20Wildlife%20Care%20Guide%20-%20Phalacrognathus%20muelleri.pdf> [Accessed 24 April 2020].

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