Allomyrina dichotoma
Allomyrina dichotoma beetles are more commonly known as Japanese rhinoceros beetles. They are a very popular beetle with children as they are easy to look after. They can be found quite easily in the wild around Japan between June and August.
The male is very easy to handle. You can hold their top horn to pick them up. They are also not so difficult to remove from your hands. If they do use their fishhook like claws to hold on, you can gently tap them on their backside and they will move forward onto any wood that you put or hold in front of them. The females are a little more difficult to hold since they don't have the horns. When you pick them up by holding their sides, they wiggle their legs quickly, making it hard to hold onto them. They only live for two to three months as an adult. However, if you care for them well, some can live up to 6 months. |
The males can grow up to 80 mm long. They are easily recognizable because of their long horn which they use to throw other males. Since they fight other males, you shouldn't leave two males together in the same container, as they can seriously injure each other.
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The chubby body is a characteristic of the female. They don't have a big horn like the males, but they a have a small bump on their head. This helps them to move through the humus. Females also have more hairs on their bodies than males to help prevent the humus sticking to their bodies as they move through the humus to lay eggs.
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Color Variations
Japanese rhinoceros beetles come in two main colors. Some are reddish while others are dark brownish. This is a type of adaptation to give these beetles a greater chance of surviving to create more offspring.
These beetles are nocturnal and come out at night to feed and mate. They can also be found in the early morning. I often find decapitated beetles near my home that were eaten by crows. The two color variations are said to be used for camouflage. The dark brownish color beetles are meant to be harder for predators to find them at night and the reddish color beetles are meant to be harder for predators to find when the sun appears. These beetles rest at the bottom of oak trees. They can be covered by dead leaves or in the humus. Their colors blend in quite well with their surroundings. The photo to the left shows a reddish male and a dark brownish female. |
Caring for Japanese Rhinoceros Beetles
You will need a medium sized container. Use a matting that prevents mites, such as the one pictured which is a coniferous blend. Put in enough matting so that the beetles can hide in it. You can use other humus, but expect there to be many mites in there.
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Add water to the matting. The matting needs to be a little moist. You don't need to add too much water, as Japanese rhinoceros beetles will spray their wet excrement around the container, keeping the matting moist.
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Add some pieces of wood for the beetles to climb on and hide beneath. You will find that a beetle will usually eat one full jelly during the night, so make sure there is enough in the container for all the beetles you have in there.
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The next day, you will find the case sprayed with excrement, the wood all over the place and all the jelly gone. Wipe down the container walls with a tissue and replace the jelly. Their excrement is smelly, so you may need to replace the matting every few weeks to avoid stinking up your home.
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You should never put two males in the same container, as they will constantly fight for food and mating rights. The males use their horns like swords and also to fling other beetles. It's okay to have one male and two females in the same container.
Children enjoy watching Japanese rhinoceros beetles fight, but it could lead to one of the beetles getting injured. |
Breeding Japanese Rhinoceros Beetles
Since the Japanese rhinoceros beetles only live for two to three months, they are very active. The males will constantly chase the females around the container. The male will mount the female to fertilize her eggs. The best time to breed Japanese rhinoceros beetles is around the middle of July in Japan. Allow the male and females to be together in the same container for about a week. These beetles are nocturnal, so you won't see much activity during the day, but at night they make a lot of noise chasing each other and trying to fly in their containers.
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This humus is very cheap and produces fairly large larvae, so it's a good substrate to use if you want to breed rhinoceros beetles. On the downside, it is quite smelly and there always seems to be fruit flies in it.
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Fill a medium to large container with a little bit of humus. Use your fist or jar to compact it. It should be compacted to a depth of about 5 cm. Most of the eggs will be laid on top of this area.
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Top the container up with more of the humus. This humus doesn't need to be compacted. Make sure the humus is moist, but not overly wet. If you squeeze the humus in your hands, it should stick together.
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Add some beetle jelly and the female rhinoceros beetle. This female should lay between 20 and 30 eggs in this container. When she has finished laying her eggs, the female will die soon after.
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Japanese rhinoceros beetles are very easy to breed. Sometimes the female will even lay eggs on top of humus that is only a couple of centimeters deep.
The female to the right laid six eggs in her container. The humus was very shallow and saturated with excrement. You can see one of the eggs sitting on top in the bottom right-hand corner of the container. Eggs start off round, but tend to be more oval in shape. |
Caring for the Larvae
The eggs will start hatching around two weeks after they were laid. It is best just to leave them alone. For the first two weeks after hatching they are known as first instar larvae. Then, they will start their first molt and become second instar larvae. A few weeks later, they molt again and become third instar larvae. It is okay to keep all the larvae together in a big container, provided that you have lots of humus for the larvae to eat. If you want to produce large beetles, it is best to put the larvae in individual containers.
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To make large males in particular, you should look at putting them in a container that has a volume of at least 1400 mL. Fill the container to a quarter of the way with the humus it hatched in so as not to shock the larva too much with change. Then fill the container with fresh humus and use your fingers to make a little hole In the middle. Gently place the larva in the hole and cover it with humus.
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Many sources state that you should avoid holding the larvae, as they find your touch hot. Other sources say that if you do hold them, make sure your hands are free of soaps and other chemicals. If you are worried about this, use a spoon to move your larvae. If you have many larvae, it is a good idea to label your bottles so that you can remember what you have done.
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To become large, the larvae will eat a lot of humus. If there is a large amount of feces on top of the humus, you should look at removing them. You should change the humus once in autumn and again at the start of spring. Keep topping up the container with humus when it becomes depleted. The humus also needs to be kept moist. Too much water is not good. It is best to keep the humus on the dry side than the wet side.
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The larvae will start to make a pupa chamber in May, Unlike other beetles, they make vertical pupa chambers. The tall containers to the right are perfect for this.
They remain as a pupa for about a month before emerging as an adult. It takes about a week for the exoskeleton to harden. In that time, the rhinoceros beetle will remain in its pupa chamber. When it is ready to emerge, it will dig its way out. |
Japanese rhinoceros beetles need to build their pupa chambers vertically. The larva above has made a horizontal pupa chamber, which may lead to deformities and even death after it tries to emerge as an adult.
A possible reason why the larva is unable to make their vertical pupa chamber is because the humus it's in might not be deep enough for them. To avoid this problem, use tall containers that are topped with humus. |
If the pupa is not vertical, carefully remove the affected pupa from the chamber it made and place it in a cup that has been lined with a couple of sheets of wet kitchen paper. Make sure the kitchen paper is not soaking wet. It just needs to be moist. The pupa needs to be able to stay vertical in this cup. If it ends up horizontal again, it means the cup is too wide.
If the affected pupa was a male, you might find that its horn is already bent. Unfortunately, there is nothing you can do to fix this. |
Put the cup in the container the pupa was in before. This container will help to keep the kitchen paper moist and stop unwanted pests or things from causing more damage. Give it a spray with water if the paper gets too dry.
Once the pupa turns into an adult beetle, don't remove it. It needs to stay in this cup for a week or so to allow its exoskeleton to harden. If you touch it in this state, you might cause deformities to its exoskeleton or even kill it. When the beetle is ready, you will see the beetle crawling out of the cup by itself. |
Finding Japanese Rhinoceros Beetles
Japanese rhinoceros beetles can be found where there are big oak trees in Japan. In the wild they eat the sap from these trees. They are easily found in July and August. They are best found at nighttime between the times of 5pm and 7am.
In summer, I grow tomato plants and I sometimes find the Japanese rhinoceros beetles snacking on my tomatoes. Even though you are more likely to find them at night, you may be able to find them during the day if you are lucky. |