INTRODUCTION

Dinomyrmex gigas (Latreille 1802) is one of the largest ant species of the world, living in the South East Asian rain forests.

This species can be easily recognised by its size. It is black in color, except the gaster, which can vary from bright orange to reddish brown to light brown.

Its habitat ranges from the South of Thailand, the mainland of Malaysia, Singapore, the islands of Sumatra, Java and Borneo as well as the Philippines. They can be found in areas ranging from peat swamps of the mangrove forests up to the mountain forests at 1500 m above sea level.

For many ant keepers and ant lovers, they are considered a dream species, one of the holy grails.

SUBFAMILY / GENUS

Originally named Formica gigas, this species belongs to the Formicinae sub-family, Camponotini tribe.

Based on its phylogenetic position, it has been considered to be on a separate lineage from both Camponotus and Colobopsis, as such, Dinomyrmex has been resurrected as a genus.

And now includes a subspecies as well, Dinomyrmex gigas borneensis, a species from South Borneo, characterized by its yellow legs.

Dinomyrmex is a distinctive camponotine, confined to southeast Asia, and recognized by the combination of very large size, elongate antennae and legs, and the presence of a metapleural gland.

The species also has characteristic mandibular dentition, with teeth occurring on both the masticatory and basal margins of the mandible.

SCIENTIFIC/COMMON NAME

These ants are commonly known as Giant Forest Ants, but during my research I also found someone referring to them as Terror Ants, which I found curious. It was only after doing the usual research of the etymology of their scientific name that I realized why it was.

Dinomyrmex is the combination of dino, from Ancient Greek δεινός (deinós), meaning “terrible, awesome, mighty, fearfully great” and myrmex, from Ancient Greek μύρμηξ (múrmēx), meaning “ant”.

Gigas is derived from the Greek word γίγας (gígas), meaning "giant".

As such it can be translated as the Terrible or Mighty Giant Ant, depending on how you want to look at them.

In terms of comparing them with some of the other largest species I have already been able to photograph, I have made this side by side image composition for your reference. What absolute beasts they are! Unfortunately the D.gigas queen kept her head tucked in, as such I believe she is few mm’s shy from the 30ish mark, as further described.

DISTRIBUTION

As already mentioned, they can be found in the following countries: Borneo, Brunei Darussalam, Indonesia, Malaysia, Philippines, Singapore and Thailand.

Not sure why Myanmar is also being highlighted as being part of their native range, because it is not mentioned in the description of their distribution list.

CASTES AND MORPHOLOGY

From “The Organisation and some Ecological Aspects of the Giant Forest Ant, Camponotus gigas” - Figure 3

Dinomyrmex gigas is comprised of our different castes and every caste has its specialized tasks as usual in most ant species. Workers are bimorphic. The castes differ in morphology particularly by allometric growth of the head.

Worker ants (minors) - A largest percentage of the colony population comprises this caste, circa 95%. The size of worker ants ranges from 20 mm to 25 mm. Except for nanitics which may have smaller sizes.

Majors - Unlike the workers, the majors have enlarged heads, which are about 2.5 times bigger than those of the workers. The average length of a major is 30 mm.

Males - The males are the smallest. with an average length of 20 mm. The head of the male is far smaller than that of the rest. Three ocelli are obvious, located in the rear central portion of the head. The gaster is not an oval shape but sharper and slimmer. The dorsal part of the thorax is raised as it is ﬁlled with ﬂight muscles. Unlike ants of other castes, this one is entirely dark brown in color.

Queen - Queens can achieve a length of 35 mm, with big oval gasters. Ocelli are present.

Although larvae are not considered a caste, nevertheless I found this interesting piece of information, which I would like to share.

Larvae appeared to fall into five clear size classes on the basis of head-capsule width (and length), probably representing separate instars. According to Holldobler & Wilson (1990) the common number of instars in ants is four, but is five in certain species. It seems that in Dinomyrmex, there are 5 larval instars as well. In well established colonies, there is presence of all larval stages (instars) at any given time.

DIVISION OF LABOR

Since this species is exclusively dimorphic with absence of intermediate worker castes, their labor division is very straightforward.

In Dinomyrmex gigas, minor workers typically do most of the foraging while majors can be recruited upon the discovery of a rich food source.

Dinomyrmex gigas Queen caring for a pupae

Otherwise, majors will primarily remain around the trail system and the areas around the nest entrances caring for colony defense.

LIFE CYCLE

There is not much available information on this topic, and although I have my own colony now, I haven’t had given myself the trouble to log their life cycle yet. I will return to this ecology guide at a later stage to revise it once I have such information.

But I did find a couple of simples time references:

1 - “After three months in their isolated nests five queens of Dinomyrmex gigas were still alive, two of them had eggs and one of these also one pupa.”

2 - “10 months after the queen had been caught it, the colony was comprised of six workers, four pupae and three larvae.”

Overall for this species, growth is considered slow.

REPRODUCTIVE STRATEGY

Dinomyrmex gigas is considered a monogynous species and founding in is claustral.

Dinomyrmex gigas newly catched Queen (Owned and Copyright by MARK)

There are reports of other keepers not getting any interest or reaction from their Queens when offered food. But in my case, I did see one Queen feed on a mix of rock sugar and water. Not sure if this was a fluke, if she was too depleted, and not following the norm.

NESTING PREFERENCES

The Giant Forest Ants are known to nest most commonly in the ground at the base of large trees, in the soil between the buttress roots of emergent trees or in fallen logs.

From “NESTING AND COLONY STRUCTURE IN THE GIANT FOREST ANT, CAMPONOTUS GIGAS” Figure 1

NEST AND COLONY COMPOSITION

Dinomyrmex gigas occupies a central place foraging role in which it follows a polydomous colony structure, and combines efficient communication and effective recruitment systems to optimize its foraging yield.

The colony structure can be flexible, normally comprising between 8 and 14 mostly subterranean nests for well established colonies, on average the size of each different colony can range from 200 to 1,500 individuals.

A common reason for polydomy that is found in various ant species, is due to the colonies having too small nest sites that can not be enlarged in any way (e.g., silk nests, tree holes).

This is not the case in the ground nesting giant ants that should be able to dig nests of any size.

Dinomyrmex gigas worker

Dinomyrmex gigas queen

In Dinomyrmex gigas, polydomy seems to be an integral part of its “dispersed central-place foraging” strategy, based on foragers searching the forest from single nests that are connected via trunk roads to the central nest of the queen.

Pfeiffer and Linsenmair (2001) studied the life history of Dinomyrmex gigas in detail, providing the following information:

“The best studied colony had a territory of 0.8 ha and a population of ca. 7000 workers, distributed unevenly among an average of 11 nests…”

TEMPERATURE AND HUMIDITY
This ant species has a low tolerance of high temperature. which is one of the reasons why it is not seen in open areas.

They are unable to cope with the high temperatures and low humidity in the canopy during the day.

Experiments in the laboratory showed that this species cannot tolerate more than 1.5 hours at 34C.

In all cases, Dinomyrmex gigas could not survive for more that 48 hours in captivity although they were kept at normal temperature (28°C) and were fed with honey. This shows that Dinomyrmex gigas has a low adaptation towards changes in the environment.

And this is one of the hypotesis of why Dinomyrmex gigas is mainly nocturnal.

FORAGING

Levy (1993) reported that this species was 93% nocturnal, having the highest levels of activity at 3.00 am. ,6.00 pm. and 10.00 pm. Through night time many workers commute between the canopy and the nests and return home by dawn.

Dinomyrmex gigas foragers collect mainly honeydew (90%) with the remainder consisting of insect prey and bird droppings.

FEEDING PREFERENCES

Like other ant species, Dinomyrmex gigas is omnivorous. This ant was seen feeding on almost anything found in the forest like fruits, dead insects, extraﬂoral nectaries, food bodies and carcasses. Arthropods and birds droppings definitely contributed to the ants nitrogen supply.

Dinomyrmex gigas feeding on a cockroach

However, in a different study by Levy (1993), Dinomyrmex gigas was reported to be a fungus specialist.

A fascinating piece of information I cannot wait to try it out as soon as possible.

DOMINANCE AND AGGRESSION

Ants from very distant nests of the same polydomous colony caused extended and intensified antennation, but were never attacked, but ants from alien colonies either displayed avoidance behavior or immediate aggression, resulting in several ants circling and attacking the alien, which was killed and/or carried to the nest.

This species is known to exhibit territorial behavior with long-lasting ritual ﬁghts between major workers, both interspecies and intraspecies. Ritual battles will take place at a ﬁxed tournament location and can last for hours every night.

NUPTIAL FLIGHTS

In temperate latitudes the reproduction of ants follows an annual cycle. The development of reproductives ends in summer and climatic conditions can trigger swarming within a narrow time-window. But this does not occur with Dinomyrmex gigas since they are tropical ants that live in a more or less constant environment.

Dinomyrmex gigas shows phase shifted reproductive cycles and a semi annual period of 188 days between nuptial flights, which points towards a strong endogenous (internal) component. This is because of the favorable tropical climate, reproduction is possible during all seasons.

Theoretically, a synchronization of the mating flights of Dinomyrmex gigas is still possible through a semiannual development cycle of the reproductives with some lunar component. Rainfall also seems to have some effects, with most of the flights followed after heavy precipitation.

MY OWN EXPERIENCES KEEPING DINOMYRMEX GIGAS

Hope you have enjoyed this article so far.

Now its time to plunge into my actual experiences, starting from the beginning which is, how did I came to acquire this species.

In June 2023, a local beetle keeper contacted me because he had caught some Dinomyrmex gigas queens in Malaysia.

And he wanted to know how to keep them. I had absolutely no experience with this species, so I gave him my best suggestions on what I thought would work. But I warned him that these were extremely difficult to care for.

I honestly thought that a beetle keeper keeping ants for the first time and jumping immediately into Dinomyrmex would have absolutely no chance to succeed. I didn’t offer to buy any because I wasn’t interested at the moment, too busy with work and life.

He kept sending me updates, and I couldn’t not believe my eyes! The Queens were laying eggs and developing well.

He was kind enough to invite me to his house. So we met in middle August 2023.

I was shocked once I entered.

The room was filled with beetles of sorts and kinds, cups and boxes everywhere… He immediately jumped to show me the ants, and said that he didn’t have interest in keeping ants, that he was only doing so because he had the opportunity to face a Dinomyrmex gigas nuptial and so he had caught some queens. He wanted me to take them.

Long story short (months actually), we agreed on a price and with the promise that I would return middle October 2024 to collect them, because once again life has been busy for me. The deal included several things and in the end I walked away with one worker colony Dinomyrmex gigas and two other separate single Dinomyrmex gigas queens with brood, everything looking amazing!

Dinomyrmex gigas young colony

Now, here comes the crux of the question: how did a beetle keeper with zero ant keeping experience turn out to be so successful?

His room! His room had two temperature control fridges and air con on 24/7 at constant 22C dedicated for his beetle keeping. Curiously, they also turn out to be the perfect conditions for the ants!

The containers for the ants were nothing special to be honest. A deli cup with breeding holes (very low ventilation), humid coco fiber as substrate, a feeding dish and that is it.

It was all about the temperature in my opinion, and now after my research, I think it is proven to be right.

The low ventilation, high nest humidity at constant low temperature were the perfect conditions for the ants to develop.

After the visit to his house, I started to recall my ant keeping experiences (particularly failures) and started to reconsider my whole approach not only for the ants, but also for the cockroaches.

I came to the conclusion that I was keeping some of my insects excessively warm. And so I bought a small temperature control fridge 90L and I am now in the process of getting another 450L fridge in preparation of the coming summer.

For the colony itself, it has been doing great.

It had a minor set back, during the process of nest changing and adding an arena, the small pile of brood was lost.

It was on a worker’s mouth and as I was picking this worker up on the tweezers, it dropped everything on the ground, and I never was able to find them.

But luckily, I managed to find a Chinese online seller who sells D. gigas pupae for brood boosting, so I got 5 pupae to make sure nothing would happen to the colony.

The colony (5 worker strong) immediately accepted all the pupae and some actually ecloded successfully soon after, bumping the total count of workers to 8. 2 pupae ended up failing and were destroyed and discarded.

In the meantime, the Queen has again lay eggs and has now a beautiful pile of 5 or 6 eggs, if I counted them correctly

You may be wondering what happened to the other two queens. Both turned out to be unmated, as their brood developed into males. One has since perished, but another queen is still alive and continuously laying eggs and trying to grow them. I am also continuously feeding her, as she is also a good photographing subject.

CONCLUSION

Hope you have enjoyed reading this post, I had an amazing time compiling this information and learned a lot.

Thank you once again for stopping by and taking the time to read. Please let me know if you have any comments, drop them down below!

Hope to see you in the next one!

Cheers!

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