Cyclommatus Metallifer Finae

Cyclommatus Metallifer Finae, more commonly known as the golden metallic stag beetle, are found in Indonesia. They are very popular among breeders due to their impressive looking mandibles which can grow to be longer than their bodies. They also come in multiple colours and are easy to breed.

They are quite docile but can act aggressively at times. Their bites are not very painful despite how their mandibles look. They do fly at times so watch out when handling them!

For ease of reference, we normally label them as CMF, which is the short form of their scientific name.

Males vs Females

As can be seen from the pictures, the males and females of this species look very different. Males can vary between 30 to about 100mm in size while females rarely exceed 30mm in size. Females are mostly a dull black colour while males have a metallic sheen and have different colours

Credits: Sky

Colour Variations

Bronze/Gold

Black

Purple

Credits: Sky

Blue (no pic available)

Care for adults

Keeping adults is relatively simple. A tub with ventilation and sufficient space for them to walk around would suffice. The first layer of the tub would be your substrate (such as soil, moss or even shredded tissue), deep enough for the adults to bury themselves. Place some bark on top for the beetles to grip onto if they happen to flip around as they can die of exhaustion if they cannot flip themselves back. Lastly would be the beetle jelly. Simply change the jelly when the beetle has finished it or when it dries out. CMF adults can survive in temperatures ranging from 18-28 degree Celsius. Avoid direct sunlight or temperatures above 29 degree Celsius.

Mating

These beetles are easy to breed. Simply introduce the male from behind the female and they will mate. Do not be anxious if they do not mate immediately as they may not be ready, just try again another day if the male shows no interest or the female runs away. Separate them immediately if either shows any signs of aggression.

Egg laying method

Things you will need:

1) Tub of at least 1000cc (1cc=1ml) with ventilation holes

2) Flake soil

3) Some bark and beetle jelly

To start off, mix the flake soil with water until it becomes sufficiently moist (it should not be dripping wet). Add moist flake soil to the tub and compress. Fill up the tub with compressed flake soil, leaving a little space at the top for the beetle jelly. Place some bark on top of compressed soil and add beetle jelly. Lastly, place your mated female into the container and close it. Ensure that the container is well ventilated (poke holes in lid). Leave the container and female undisturbed for around 2-3 weeks before pouring out contents and sieving through the soil to search for eggs.

Collect eggs and place them in a different container filled with flake soil. Remember to put the flake soil back into the original tub, there are 2 reasons to do so:

1) you may want to put the female back in to lay more eggs (if so, compress the flake soil)

2) there are bound to be eggs that were missed so incubate that container for 2-3 more weeks before pouring out and sieving through to search for larvae (easier to spot than eggs)

A CMF egg

CMF eggs and larvae

A CMF L1 larva

Eggs placed in containers

Care for larvae

CMF larvae are easy to rear. Simply place them in a container filled to the brim with flake soil. Larvae should not be kept together once past L2 stage as there is risk of cannibalism or fighting. Ensure that the container is well ventilated.

As the larvae grow in size, you need to change their containers to meet their increasing food demands. Here are the recommended sizes:

L1-L2 larvae: 500cc

L3 larvae (female): 500-1000cc

L3 larvae (male): 1000-1500cc

Larvae are generally sexed when L3 as they are too small during their 1st and 2nd instar phases to accurately tell their gender. The bigger the container given, the more food and space the larvae have, enabling them to eat more and thus grow bigger. Size of the adult is determined during their larvae stages (they do not grow any more once they reach adulthood) so those aiming to raise larger adults should aim to provide larger containers and better quality food for the larvae.

Another important factor to note is the temperature at which they are raised. Fluctuating temperatures can cause stress to the larva thus they should be kept in areas with stable temperatures. They can survive between 16 to 30 degree Celsius, but do best at about 18 degree Celsius. At colder temperatures, their metabolism is decreased and they spend a longer period of time in the larvae stage. This allows them to ingest more food and thus grow bigger.

Higher temperatures = smaller adult, shorter time spent as larva

Lower temperatures = larger adults, longer time spent as larva

When choosing the containers to raise L3 larvae, do bear in mind that they do better in flatter but broader containers. Containers about 6-7cm deep are sufficient. Sturdier containers would also help larvae develop better.

Care for pupae

Pre-pupa seen from outside

Pre-pupa after opening chamber

Female pupa

Male pupa

After about 6-12 months since they hatch, the larvae will enter a pre-pupa phase, where they resemble a dehydrated larva. They move much less and barely eat. In about 2 weeks they will pupate. For newbies, it is recommended to leave the pupa chamber untouched (it is usually buried and you are unable to see the pupa). However there are ways to monitor the pupa such as opening the chamber as seen in the pictures above. There are chances of destroying the pupa chamber in the process so make sure you understand the procedure and risks before doing so.

The pupal stage usually lasts around 4-5 weeks. After about 3 weeks as a pupa, it will start to darken as it is preparing to eclose (emerge from pupa as an adult).

Dormant period

When the beetle first ecloses, their exoskeleton is still soft and will need time to dry. During this time, refrain from touching them or disturbing them. Even after drying, they will enter a dormant period and will not need to eat for about 3-4 weeks. Simply leave them as is and do not disturb.

When they are ready to eat, they will crawl to the surface and start trying to get out of the container. You can now move them to the enclosure for adult beetles and feed them.

Note: it is important to watch out for when they are ready to eat. They can starve to death if not fed in time.

Variation in jaw lengths

39mm small CMF male

81mm large CMF male

Sizes vary largly even amongst the males of CMF, though it is largely due to environmental factors such as temperature and diet rather than genetics. However larger males will pass on genes slightly more favourable for large sizes so for those aiming to raise large males, you may wish to consider choosing larger males for pairing and breeding. However it is still possible for 2 males of the same parents to turn out very different in size due to them being raised in very different conditions.

Some extra notes from experienced breeders

For those aiming to raise large males of 80mm and above, here are some recommendations for conditions to rear the larvae at:

L1: 500cc flake soil, 20 degree Celsius

L2: 500-800cc flake soil, 20 degree Celsius

L3: 1000cc flake soil, 18 degree Celsius

With that, we have come to the end of the husbandry notes for CMF. Hope these notes help and wishing you a fun and enjoyable beetle keeping journey!

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