Carebara castanea
The most amazing feature of this species is the size difference between the queen and her workers. The very small pale-yellow workers are only about 1.5 mm in size and are dwarfed by their comparatively gigantic 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 first 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 soil 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 setup.
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 aphids and small insects that live underground such as termites. At night in humid conditions the workers will also forage outside, looking for dead insects and drops of fallen honeydew. In captivity, colonies will feed on a sugar/water mix, pieces of biscuits/cake, and small dead insects.
We had been trying to cultivate colonies of this species from new queens for six years with little success. In 2019 and 2020 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 in 2021 after another adjustment, we succeeded in raising colonies from just over 50% of the new queens we had captured.
The first brood raised was between 200 - 300 workers and the follow-on brood was in the region of 600 - 800. Once these matured the colonies literally took off and progressed very quickly. Within six months of founding the queens had well over a thousand workers and a brood mass in excess of 5000.
For the 2024 season new queens will become available in April / May, and with luck established young colonies about three months later. From what we can ascertain no one else is offering this species as established young colonies. Hence young foundation colonies of this species (when available) are exclusive to our store.
Summary: A fascinating species with a large size difference between the queen and workers. Nicely coloured and once established, easy to feed. Something new to try, which will create very impressive colonies.
However: There is very little information available on cultivating this species, and they are not recommended for beginners to exotics, as colonies from new queens are very difficult to establish, and young colonies can quickly perish if not cared for correctly. Hence, they are only recommended for very experienced hobbyists.
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 we sell 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 setup 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 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 - 32°C, with minimal disturbance. It 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 of foundation they can have around 300 - 500 workers. The first batch of workers to emerge do not seem to go out to forage, but rather concentrate on helping the queen with the existing brood. Once the follow-on brood has 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 mold from 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.
Advice:
Do not use compost/soil purchased from a garden centre, 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.