Care Sheet - Rainbow Stag Beetle (Phalacrognathus muelleri)
An adult male Rainbow Stag Beetle (Phalacrognathus muelleri)
Common Name: Rainbow Stag Beetle
Scientific Name: Phalacrognathus muelleri
Distribution: Queensland, Australia
Scientific Classification:
Order: Coleoptera
Family: Lucanidae
Genus: Phalacrognathus (Macleay, 1855)
Species: muelleri (Macleay, 1855)
World Record Size:
Wild – 70.0 mm
Captive Breeding – 68.6 mm (by 森下雄貴, 2020)
Egg to adult: 4-8 months
Adult lifespan: 18 months
Pupal stage duration: 1 month
Maturation time of fresh adults: 3 months
Egg incubation duration: 4 weeks
Rearing temperature: Room temperature (18-25°C)
An adult male and female Rainbow Stag Beetle “Ghost Eye” (Phalacrognathus muelleri)
Species Description:
The Rainbow Stag Beetle, (Phalacrognathus muelleri) is a species of stag beetle native to Australia. They are known for their metallic body that shines like the 7 colours of the rainbow. Their body morphology is slightly different from the typical stag beetles such as Dorcus spp. and Prosopocoilus spp., and their mandibles are smooth and curved upwards.
They are a wonderful species of stag beetle to keep as pets as they have a glittering body, ornamental mandibles, and are not aggressive. They also have a long adult lifespan, so they can be enjoyed for a much longer period of time comapred to other beetle species.
Food for Beetle Larvae:
As with most stag beetle species (Lucanidae family), the larvae will feed on substrate that is mainly composed of decayed wood of trees in the Beech family (Fabaceae family) which include oaks (Quercus spp.), beech, (Fagus spp.) and chestnut, (Castanea spp.). A general beetle substrate guide that covers the different types of substrates for different types of beetles can be found HERE.
To raise large adults, home-made Flake Soil should be used instead of wood collected from nature. Flake Soil is the term used for fresh sawdust that has been decayed under controlled conditions with additional protein sources that results in a uniform, earthy substrate that is rich in nutrients.
To view my tried and tested flake soil recipe with a breakdown of tips and tricks, please click HERE.
Food for Adult Beetles:
Adult beetles can be fed on beetle jelly or most sweet fruits such as bananas, apples, mangos, peaches, melons and watermelons to name a few. Adult females should preferably be given fruits that are higher in protein content such as bananas to aid in their egg production.
Foods to avoid for adult beetles are certain types of sugar-water, and fruits high in acidity such as those in the Citrus genus (oranges, lemons, grapefruits, etc.). Fruits that are high in acidity are said to disrupt the pH balance in the gut of some species, potentially leading to refusal to feed after a certain period of time.
An adult male Rainbow Stag Beetle “Mirror Glaze, Amethyst” (Phalacrognathus muelleri)
Breeding Phalacrognathus muelleri:
How to make a breeding box:
Prepare a 15 L box and fill it 50% full with substrate.
Compress the substrate as hard as you can (use your hands to press it from above).
Lay down decayed spawning logs.
Lightly fill up to 70% of the container with substrate.
Place perches on the surface so that the adult beetles can right themselves up if they accidentally flip over.
Place fruits (or beetle jellies) on the surface as well.
Once the breeding box has been completed, place both the male and female Phalacrognathus muelleri together in the breeding box. Leave them together for 7-10 days to ensure that they mate properly. Afterwards, the male can be taken out and kept separately if you wish.
If the male is seen attacking the female, it is a likely sign that they are not sexually mature yet. When this hapens, keep them separately in their own enclosures for a few weeks before attempting again.
How to check for eggs/larvae:
The breeding box can be checked for any eggs and larvae 1 month after the female has been introduced into the breeding box. Find a large box and empty out the substrate from the breeding box into it by flipping it over. Carefully break apart and work through the substrate in order to find the eggs and larvae. They are soft and fragile, so please take care to handle them gently when moving the eggs and larvae.
Raising the larvae:
Larvae should ideally be separated and reared individually to prevent the larvae from getting stressed out by each other (and to prevent any risk of cannibalism in more aggressive species). Communal rearing is possible, provided that plenty of space and substrate is given. Phalacrognathus muelleri can be reared on either wood/flake soil, or kinshi bottles. At the L3 stage, the larvae should be kept in a container that is a minimum of 800 ml in size.
Pupal stage:
From the moment onwards after the larva constructs a pupal cell, it is important to keep disturbance to a minimum. Please refrain from unnecessarily picking the container up or shaking it. Their pupal period is about 1 month, after which they emerge into an adult beetle.
Photo Gallery:
An adult male and female Rainbow Stag Beetle “Ghost Eye” (Phalacrognathus muelleri)
An adult male and female Rainbow Stag Beetle “Mirror Glaze, Emerald” (Phalacrognathus muelleri)
