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Rainbow Stag Beetles(Phalacrognathus Mulleri) are a popular beetle kept in the beetle trade. However, purchasing them as adults can be quite the task. They are more widely available in the larval stage. I was fortunate enough to attain a pair of lovely rainbow stag beetles.

The Rainbow Stag Beetle originates from Queensland Australia. They are known to come in different colour varieties.  Their standard colouring is the usual shimmery rainbow colour, but they also come in a metallic green and red shade too.


Rainbow Stag Beetles are not just famous for their beautiful shimmery colours but also for the fact they have a longer lifespan than most beetles. Their approx lifespan can be between a year to two years. They must, however, receive the best care, as every animal and insect must. 

How to tell Gender

It's very easy to determine gender in stag beetles in general. They are sexually dimorphic; this means there is no difficulty in telling gender, that there are features that separate male from female.   

The females are smaller than the males, measuring around 4.5cm. A small indent lays between their head. The most distinguished feature of a female stag beetle is the pincers. Female Rainbow Stag has smaller mandibles, commonly used to chop up wood.  Males are usually around 6.8cm in size and have longer mandibles.

However, I got mine from another breeder, and unfortunately, the larvae did not form properly in the pupae, therefore they didn't reach their typical size.  Even though they have stunted growth, Blossom and Hercules were happy and well. 


Female Rainbow Stag(Blossom): Has an indent down the middle of the head, smaller body and mandibles. 

Male Rainbow Stags are bigger than the females, measuring a great 6.8 cm.  There is no indent on the head( As seen below) and mandibles are larger than the females. They are used to catch females during mating or to fight males invading their territory.


Hercules(The photo above): On the average beetle the mandibles are much bigger, longer and are curled. 

It's worth noting that Blossom and Hercules are known as minor rainbow stags as they are not the large size that a rainbow stag should be. Cosmos, Astrid and my other Raibow Stag, Devil are major beetles because they are the correct size. This occurs when the larvae goes into pupal stage too early, therefore does not eat enough to grow to the correct size.





Notice the female has smaller mandibles and is slightly smaller than the male. The male has larger mandibles and is bigger than the female.  Astrid is my biggest female out of the three.  Unfortunately, Hercules and Blossom have passed away. I do still have another male Rainbow Stag called Devil, who is a red  type( See the photos below).























I am currently attempting to pair Astrid and Devil. Hopefully, it will be a successful pairing. 


Housing Rainbow Stag Beetles: 

Enclosure and pairing. 

A female and male rainbow stag beetle can be kept together in the same enclosure. However, NEVER place two males in the same enclosure. A pair of male stag beetles will fight to the death for food and mates. I recommend purchasing a breeding pair first. You can get them in bigger groups, but to be safe, I would keep two females to one male. There is a chance that even the females can sometimes pick on each other, especially if there is a weaker individual in the group. 

Other owners tend to separate their beetles by a divider until breeding.  I recommend keeping them in completely separate enclosures as this provides them with enough room. Rainbow stag beetles are separated because male beetles can be rough when breeding and can throw the females around. By keeping them separate, the life of the beetles is extended. If you do not keep them together, you must ensure when the male has finished breeding that he remains in the enclosure for two weeks. This is to ensure that the eggs are properly fertilized. I keep mine together because they are not of the average-sized rainbow stag. Hercules's mandibles are too small to lift and throw Blossom around. The two get along just fine. 


Average Temperature: Rainbow Stag Beetles correct temperature is between 22°C-27°C. You can use a heat mat to achieve this. However, they do burrow, so use the heat mat on the outside of the tank, not the inside. They do not need daylights like Sun Beetles as they are nocturnal. You can also use those to boost the temperature, but do not purchase daylights that are too hot. A normal daylight bulb will suffice.

Humidity: Keep the soil moist but not too drenched. Spray every other day and ensure humidity is kept constantly between 70%-80%.


Rainbow stag beetles diet consists of ripe fruit like banana and apple. I would say banana is the best choice as I have fed an apple to my sun beetles and they didn't like it. I would stick to banana. Though ripe fruit is a good source of food, some breeders feel that this attracts pests and mites. Instead of fruit, I  use beetle jelly. Using the jelly guarantees a pest-free zone. 





Step By Step Guide on how to build

  a Rainbow Stag Beetle Enclosure 

1. Decide how many beetles you want:    Rainbow Stag Beetles are better kept as a pair.  However, you can also keep them in small to medium groups. When it comes to groups, you MUST only keep one male in a group. Male stags are aggressive and will fight to the death for food and mates. I recommend having two females to one male.  Females tend not to fight as savagely as males, but they sometimes can pick on other weak or sick beetles in the group. 

2. Purchase the correct housing: Before you purchase your rainbow coloured bug, you must choose your enclosure and set it up beforehand. I recommend using a medium to large cricket pen or a vivarium. Do not keep them in a net because water vapour will escape quickly, leaving the enclosure dry and cold. Also, most nets have holes at the bottom, and the soil would fall out.  Beetles like to climb and fly, but they are not arboreal, so, therefore, a tall enclosure such as a butterfly net is useless.  

3. Purchase the correct substrate: Beetles are great lovers of burrowing into the soil. You should get chemical, pesticide-free soil. For Stag beetles, fermented flake soil is highly recommended for substrate and to raise Rainbow Stag Larvae. 

Breeding:   Stag Beetles lay their eggs in rotten oak beneath the soil. It's best to place the logs further into the soil, as it makes the female more comfortable laying her eggs.  Females will drill a hole in the logs and lay their eggs there. They are also known to lay eggs in the soil, but only if it is fermented flake soil. 


  It is best to separate the male and female when they are not mating as males can be aggressive and throw females around. Female beetles have been known to lose limbs during breeding. Some breeders use a plastic divider that can be removed when they want to breed their beetles, but I find that does not give them enough room, so I would place them in different enclosures. This provides them with enough room to move around, look for food and burrow.  My beetles are not average-sized. Therefore Hercules, my male beetle, would not be able to harm Blossom during mating.

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