Formica selysi, a European ants, maintain a strict order and distribution of responsibilities by forming living "rafts" during floods.
Inhabiting Central and Southern Europe, Formica selysi ants settle along the banks of deep rivers, so they regularly encounter floods. However, they are remarkably adapted to these disasters and, when flooded, quickly fold into a living "raft". In the center of it is the uterus, and the less dense larvae and pupae are held by the worker ants at the bottom of the structure, providing it with high buoyancy. No one dies, and the colony remains intact, quickly resuming work as soon as the water takes it to a new location.
This interesting form of behavior was studied by American and Swiss scientists led by Professor Michel Chapuisat. The results of the work are published in the journal The Science of Nature. The authors managed to show that on a living "raft" not only the queen and the young, but also each ant has its own place and role.
Scientists selected ants from 25 colonies that live on the banks of the Rhone and experimented with them in the laboratory. Each group, whose members were marked with colored dyes, the researchers placed in a separate transparent formicarium, and then set up a small flood. As soon as the ants realized the danger, they quickly folded into their "rafts", and video cameras monitored the behavior of insects in every detail.
© The University of California, Riverside
Looking through the records, scientists noticed that the place that each ant occupies on the "raft" remains constant, and in the next flood it will be in the same place where it was during the previous one. Conventionally, biologists have divided these positions into four types - from above, from below, in the center and from the side - showing that insects preserve them every time they fold a living “raft”. In this case, it does not matter whether larvae and pupae are present in the colony or not. When chicks are at hand, worker ants form a larger and flatter raft, but each still takes its proper place.
The authors find it difficult to explain the reason for this specialization, but they assume that the place of each ant may be determined by its age, size, or working specialization in the colony.