Common names: 'The Marauder Ant' or 'Asian Army Ant'
This species ranges over south East Asia from countries with distinct seasonal weather such as India, Myanmar, Laos and Thailand down to countries which have constant equatorial weather such as Malaysia, Singapore and Indonesia.
The most notable thing about these ants is the habit they have of sending out thousands of workers on long 'swarm trails' hunting for food. In mature colonies these hunting swarms can be 10,000 plus strong and resemble the famous army ants of the Amazon - attacking and consuming anything edible in their path.
This species is also well known for its large variation in the size of the individuals. The smallest workers measure only 2 to 3 mm while the largest super majors can be nearly 20 mm. There are also many intermediate forms between these sizes. The difference in size between the minor and major workers is said to be the greatest of all ant species and the super majors can weigh up to 500 times the weight of one of the smaller workers.
The smaller workers make up the bulk of the colony and do most of the work in the colony including taking care of the brood and queen. The larger major workers act as guards and food storage containers inside the nest - and when outside on the trails as heavyweight cutters.
In their natural habitat during the heat of the day the colonies are quiet but as soon as it cools down and the evening approaches they will suddenly send out thousands of workers on a quest for food. These swarm trails will attack and devour anything edible that they find. The workers make up the bulk of the hunting swarm but larger super major’s will also go hunting where they use their powerful jaws to cut up the larger prey into more manageable pieces – so it can be carried away by the smaller workers. When the larger majors go out on the trails it is common for several of the smaller workers to hitch a lift and climb onto their backs as they go along. Some researchers hypothesize this is to save energy enabling the smaller workers to get somewhere without having to walk and hence expend energy - others say it is to help protect the larger majors against predators.
They feed on a wide range of foods and seem to accept almost anything edible including seeds, meats and sugary excretions. In countries where there is a distinct dry season when other food is scarce a large amount of plant seed is collected. Large prey or excess food is frequently concealed with earthen covers, probably to help protect the ants and their food from other predators, but also allowing them to carry on dissecting any larger prey during the day.
The individual ants are very aggressive and do not retreat when challenged. If they are disturbed they have a swarm action and will immediately attack the intruder no matter how large. They do not sting but have a painful bite. The smaller workers are much more aggressive than the larger majors and will swarm over any potential food or intruder, however if the larger major workers fasten their powerful jaws onto you their bite can be extremely painful and can cut through human skin.
In seasonal climates such as northern Thailand colonies produce alates only once a year, but in climates which are constantly warm such as Malaysia colonies are said to produce alates every three months.
The alates are active at dusk and the males are too large for the females to carry, so mating occurs on the ground. The males leave the nests first in the early evening and congregate at a 'swarm site' then a few hours later the females will appear. When the females arrive at the swarm sites they are immediately mobbed by the males all trying to mate with them. When a male encounters a female he 'buzzes' her with his wings making an audible sound and quickly mates with her. Females will copulate with several males and from personal observations a queen will not remove her wings until she has mated with 5-7 separate males.
Newly mated queens starting their own colony will dig a chamber in soft earth at a depth of about 15 cm, where she will raise her first brood. Within six months the young colony can be several thousand strong and actively hunting with small swarm trails. Young colonies in the wild will also quickly produce a small number of majors which will act as food storage reservoirs.
In the nest the fertile queen is constantly guarded and groomed by the small workers - and if a colony is disturbed the workers will rush to the queen and completely cover her presenting any potential predator with a seething mass of biting ants.
There has recently been a lot of discussion / confusion regards the number of queens a colony of this species has. In all the wild colonies that I have excavated I have only ever found a single queen. I have also observed that when new queens are placed together they will fight resulting in the death / maiming of all but one. The confusion regards the number of queens in a colony seems to arise from the frequent imports of colonies called C. diversa from Chinese wholesalers. The Chinese colonies sold under this name are usually the closely related species called C. affinis, which has multiple queens in a colony and is much easier to obtain and can also be split up to maximize profits. Queens of the true C. diversa are much larger and more robust than those of C. affinis. The size difference is notable and can be used as a distinguishing factor as C. diversa queens are circa 2.2-2.4 cm in size, while the queens of C. affinis are only 1.5–1.8 cm.
They are vigorous excavators but also will often use burrows of other insects and small animals to construct a deeper nest. Wild nests can often extend to 60-75 cm plus into the ground. This may not seem very deep but taking into consideration that the smaller workers are only 2 mm it’s quite an achievement. Nests are usually located in open areas where they can benefit from the warming action of the sun.
Due to the size of the colonies in time they will frequently consume all food resources in a particular area and they will then move their whole nest. This is usually done at night over a period of several days. The new nest locations can be significant distances from the old nests – one colony I followed from a flooded rice field was relocating over fifty meters away. The workers will move the majority of the brood and work force first, then usually in the early hours of the morning the queen will move accompanied by a guard of super majors.
In the wild they are attracted to moist places where more potential prey can usually be found and where trails can easily be covered with earthen defenses. In dry seasons they will frequently appear near irrigated farmland and near houses after gardens have been watered.
In captivity they need a large foraging area and a plentiful supply of food. The individual small workers do not have a long life and to successfully replace and increase the work force it is essential to provide optimum conditions for the colony.
The temperature of the central nest chamber should be as near to 28-32 degrees Centigrade - but there should also be a temperature variation gradient so they can choose their own preference.
Humidity is very important for this species and colonies kept in very dry conditions will quickly fade away. Keeping a cover over the colonies container allows the humidity to build up and regular sprays with a fine mist sprayer will quickly bring humidity levels up. The incorporation of some quick growing plants will also help increase the humidity. It is also essential to always ensure that the colony has access to water tubes.
The level of humidity has however been over stated on many forum sites in the past, with the result that colonies are often kept near saturation point - which is detrimental. Moisture must always be available but not to the point of being wet. The formation of moulds on uneaten food is a sure sign that the humidity / ventilation level is incorrect and needs adjusting.
Ventilation is also important and the incorporation of sliding escape proof vents will allow you to ventilate the habitat container during the day light hours when the colonies are less active. In their natural environment the humidity is high at night at around 70-90 percent depending on the season and low during daylight hours when it can fall to 40-50 percent. This natural humidity variation helps prevent moulds forming, which if left can quickly infect and destroy the colonies brood.
Food should always be available and should be varied. This species seems to eat a wide range of items. Foods that I regularly feed my colonies includes shortcake biscuits, tuna chunks, other ants brood, termites, small seeds, pieces of cake and a wide variety of dead insects.
During the dry season when other food is scarce colonies will collect large amounts of seeds and it has been recorded that over 50% of their food intake at these times consist of various seeds.
Once a colony has grown to a large size and to stimulate production of alates they will need extra protein in the form of small animals / invertebrates such as dead lizards, pieces of uncooked chicken, baby mice etc; a strong colony can reduce a full grown gecko to a perfect skeleton overnight.
When all these conditions are met the queen will produce a mass of brood and the colony should increase in size quickly. A strong healthy colony will have a large amount of brood and healthy larvae should have a glistening appearance.
The workers brood cycle is quite quick with eggs hatching in 9 days, larvae pupating 9 days after hatching and callows emerging after another 10 days. The brood cycle for the majors is longer and can take up to 45 days to complete. The brood is very fragile and easily damaged - so great care should be taken when manipulating and moving colonies.
I have managed to successfully cultivate this species and have colonies raise alates in semi-natural set ups. These consist of a glass aquarium tank with a shallow 1-1.5 cm layer of humus / soil, landscaped with large branches, pieces of bark and dead leaves. An artificial plaster / gypsum nest is then either placed on the floor or side of the tank allowing you to see into the colony. By adjusting the humidity of the foraging area and nest you can ensure that the colony stays within the nest. If the colony moves into the soil medium simply allow the medium to dry out a bit and keep the artificial nest moist and they will move back.
They are very difficult to keep in clinical set ups without any medium. If you are going to try and use one of these set ups, give them a few spoonfuls of soil. They will then use this to adjust the entrance size and if required block up any excess ventilation holes, - this allows them to adjust the airflow and humidity level in their nest.
Considerations when buying:
Many suppliers sell queens with only a small number of workers which can easily die before a new brood is raised. When you buy a colony try and obtain one with a minimum of 500 to 1000 workers and ensure that some large majors are included. These will act as food storage buffers - absorbing food in times of plenty and slowly releasing it back into the colony at a steady rate ensuring a steady flow of food is always present. It is also essential to ensure the colony you buy has a good amount of brood to ensure that new workers are continually emerging during the establishment stage.
It is difficult for general suppliers to maintain this species without extra care and frequently colonies are offered which are on the point of collapse before they are purchased. This has given the species a reputation of being difficult to care for.
We would strongly advise you against purchasing 'cheap colonies' that only have a few workers as they will frequently fail. This species breeds quickly so in all probability these smaller colonies are already close to collapsing and although they initially seem good value in reality they are a waste of money. The only time such small colonies should be considered are if they are natural ‘new foundation colonies’ and even then colonies with just a few workers are recommended only for very experienced hobbyists.
The first six weeks are the most crucial after obtaining a new colony. Within this time the colony has to raise a significant number of new workers to replace the old ones. The brood cycle from egg to new worker takes about four weeks, and you have to allow enough time for the queen to resume egg laying after the disturbance of transport and for a significant number of new workers to emerge. Once this has been accomplished and the colony has a credible force of new workers then it will be over the critical establishment period.
Those hobbyists that are successful in establishing a colony occasionally report that the colony fails after about a year. My personal observations of their natural conditions suggest that they will benefit from a winter rest and should not be kept at the same stable temperature all year around.
In northern Thailand there is a distinct cool season where night temperatures regularly fall to 10-15 degrees C. This stimulates the colony into a state of semi dormancy. Although this slows down the brood development it also slows down the metabolism of the ants so they will live longer - balancing out the longer time the brood takes to develop. It should be noted that during this time although the night temperature falls the day temperature is still 25-30 C - so they will still forage in the early evening and the brood will continue to take food. A duel night / day thermostat on your set up should enable you to simulate this winter rest which occurs for about six weeks during Dec/ Jan.
This rest period seems to invigorate the colonies and once the temperatures are raised again and more food fed, they will frequently raise a brood of alates. All my colonies are subjected to these natural conditions and thrive.
Summery: This is a fascinating species to keep with habits similar to army ants. They are however a challenge to maintain. They require a large nest / habitat area and a constant / varied supply of food. With this in mind we must stress that they are really only suitable for hobbyists who have had previous experience at keeping exotic species.