Unlike most ant species, the dark guest ant is not able to produce worker ants, those individuals that are responsible for searching for food and caring for the brood. This means that the only way this particular ant can survive is by enslaving the worker ants of another species, Tetramorium ceaspitum (known as the ‘pavement ant’, due to it frequently nesting in pavement cracks) (3) (5).
The dark guest ant is an extreme example of an ‘inquiline’, that is, an animal that lives in the nest or burrow of another species. A queen dark guest ant, which has just mated, invades a Tetramorium ceaspitum colony and becomes the new queen (3) (4). It is not clear whether the female achieves this position by taking over an old, queenless colony, or by influencing the Tetramorium ceaspitum workers to kill or starve their own queen (8). The loss of the Tetramorium ceaspitum queen means that no more host workers are produced, and because the dark guest ant now relies on these to survive, the dark guest ant colony can only exist for as long as the worker colony does, typically for two to five years. The queen, which is now swollen with eggs, reproduces quickly in order to secure the next generation (8).
The Tetramorium ceaspitum workers now forage for food for the new queen and her brood as if they were their own. These workers are predators and scavengers of animal and plant material, in particular seeds (8).
As the male dark guest ants are wingless, pupa-like and unable to leave the nest to find unrelated females, they mate with their female siblings in the nest (5). After mating, the females fly out of the nest in search of a new Tetramorium ceaspitum nest to invade (9).