The most amazing feature of this species is the size difference between the queen and her workers. The very small pale-yellow workers of this species are only about 1.5 mm in size, and are dwarfed by their comparatively massive orange / reddish queens which are 2 cm.
Alates fly in the early evening at the start of the rainy season - usually a day after heavy rain. The new queens found colonies independently, digging deep into the moist ground where they construct a small round foundation chamber. Because of the size difference between the queen and the workers the initial brood raised by a healthy queen can be in the region of 200-300 workers, which is a very large brood for a queen to raise without any additional food.
New queens dislike disturbance and don’t seem to like artificial foundation nests. In captivity if kept in artificial nests they will frequently abort their initial brood and subsequently die. Some success however has been obtained by keeping them in small containers of earth until they have raised their first workers, – then when the queen has a good workforce to care for her and the brood, the young colony can be moved into an artificial set up.
In the wild they construct large nests deep in the ground usually near the tangled roots of trees. The small workers forage via underground tunnels and outside at night under surface leaf litter. The central part of their nests seems to be constructed of fine soil particles bound together by saliva and has a delicate cardboard type texture.
Their exact natural food source is unknown but expected to be the secretions from root aphis and small insects that live underground such as termites. I have occasionally seen workers out on the soil surface at night - which presumably have been foraging for dead insects and drops of fallen honeydew.
Note: Our captive colonies are feeding on a sugar/water mix, pieces of biscuits / cake, and small dead insects!
There is very little information available on cultivating this species and colonies seem to be quite difficult to establish. Hence, they are only recommended for very experienced hobbyists.
This is a species that does not seem to have been raised and successfully kept in captivity past the initial foundation stage. It is a challenge even for experienced keepers. However, if someone does succeed in cultivating these - the colony would be very impressive.
Update June 2021:
We have been trying to cultivate colonies of this species from new queens for six years now with little success. The last two years we managed to get them to raise new workers, but they never foraged and just seemed to fizzle out. Every year we have made slight changes to our cultivation method, learning from our past mistakes, and this year after another adjustment it finally looks like we may have succeeded.
For the first time we have workers out foraging, and the colonies have a large follow-on brood. The new brood mass after the first workers emerged is in the region of 500 plus. This batch of brood should mature over the next 3-4 weeks, and then they will have a good strong workforce. We will then consider it a success - and will be able to release the first young colonies for sale.
These are exclusive to our store. From what we can ascertain no one else is offering this species as established young colonies, and no one is keeping them in captivity.
Something new to try - which will be very impressive!
Raising colonies from new queens
It is very difficult to establish colonies of Carebara castanea from new queens. The queens dislike any kind of disturbance during the foundation stage. If you check on them frequently, they will eat their eggs and fail to establish. If possible, limit any observation to just once a week, and do it in subdued light, handling the container very carefully.
The queens are posted in test tubes, but we do not recommend leaving them in the tubes to establish colonies. I have tried many times to keep them in test tubes to start colonies, and they have always failed.
They also dislike artificial nests. Being in an open chamber gives them a feeling of lack of security, unlike an enclosed natural earthen foundation chamber provides. If you are going to try and establish a colony in an artificial nest. The only suggestion to help is to place some moist soil in one of the chambers, and the queen will use this to create a more natural chamber.
The ideal foundation set up is a small container filled with moist earth. If the container has transparent sides and the outside is covered with a dark cover, they will often dig down and build their foundation chamber against the side - so you can still see what is happening. Alternatively, and esp. for those queens that already have some eggs, fill a container with some earth, lightly compress it, water it slightly, then make a small chamber on the surface and cover this with a piece of glass, covered with something to keep the light out. This chamber should be approx. 2-3 cm max wide and a 1.5 cm deep. You can then place the queen and eggs into this. If she is happy after a few hours, she will have modified the chamber to her requirements and settled down to raise her brood. Keep the medium moist not wet, temperature circa 28-32C, with minimal disturbance. They will take 4-5 weeks to raise their first workers.
Their first brood can be a significant size and if looked after correctly within about three months they can have around 500 workers. The first batch of workers do not seem to go out to forage, but rather concentrate on helping the queen with the existing brood. Once a few hundred workers have emerged they will start foraging – usually at night. Feed them on a sugar / water mix or diluted honey, and small dead insects. Remove all uneaten food after 24 hours to stop any molds forming.
If they do successfully establish a colony, we advise keeping them in the earth nest until they have a good-sized workforce, then if required carefully move them into an artificial nest. We recommend placing a few small spoonful’s fine-grained moist earth in the outworld, which they will use to adjust the entrance and chamber size, and this also enables them to control airflow / humidity. During the moving phase keep them humid as the small workers can desiccate easily.
If you succeed in raising a colony, do please let us know! You can be justifiable proud of your achievement.
Advice: Do not use compost / soil purchased from a garden center, as these often have added insecticides incorporated.
Do not feed with any insect that you have found that is already dead, as it could have been killed by insecticide, and still have some poison in its system.
Do not keep the foundation container near anything that vibrates, such as fridges.
Do not keep the foundation chamber where it will be subject to periods of direct heat or sunlight, such as on windowsills or near radiators.