European ants can carry a young queen to a nearby nest to mate with as distant relatives as possible.
The ant colony consists almost exclusively of females. However, only one of them - the uterus - reproduces, and the rest modestly perform all working functions (although sometimes some may also become fertile). It is not easy for this "queen" to find a suitable mating partner. And it's not a shortage of applicants: she is constantly surrounded by males from her own nest. However, communication with them is fraught with all the dangers of inbreeding, closely related crossbreeding. Therefore, the queens of most ant species mate only once in their life, during the mating flight, when they meet males from other colonies.
Another unusual mating mechanism was discovered by biologists from the University of Regensburg who studied the southern European ants Cardiocondyla elegans. The queens of these insects are delivered to suitable partners “by hand”: sterile workers carry them to a neighboring nest and leave them on the doorstep. Mathilde Vidal and her colleagues write about this in an article published in the journal Communications Biology.
During 2014-2019, scientists have localized 175 colonies of Cardiocondyla elegans living in the south of France. Observing them, biologists recorded a total of 453 cases of such "matchmaking" of ants. Despite the tiny size of workers, they sometimes carried queens up to 15 meters before leaving at the gate of another nest. No one expected them back: after spending a season in a strange anthill, such females are expelled and soon become the founders of a new colony.
Judging by the almost straight trajectory of the movement, the workers who carried them to "woo" knew exactly where to go. Sometimes they even walked past closer nests to reach their goal. By comparing the DNA of neighboring colonies, scientists noticed that the ants choose those that are more genetically distant from them. Obviously, this avoids inbreeding, which can destroy the entire colony. However, it remains unclear what exactly workers are guided by when choosing a suitable nest, and how they determine genetic affinity with its inhabitants.