By working together, ants can do things that would be unachievable as insects on their own. From tackling prey hundreds of times their size to building bridges in order to cross a stream, the collective nature of an ant colony is what has led many to refer to them as a “super organism.” It was this latter skill in self-assembly that captured the interest of researchers from the University of California, Riverside, who have been studying how ants assemble to form living rafts in the event of floods.

They’ve discovered that when the ants gather to create the floating platforms, which are then loaded with the queen and the larvae, individual insects will repeatedly take the same position within the living raft. This, say the researchers, is the first time that memory has been demonstrated with such forms of self-assembly. The researchers hope that their discovery could be used to improve swarm robots and microbots, which are typically based on ants and other social insects.

“These elaborate rafts are some of the most visually stunning examples of cooperation in ants,” says Jessica Purcell, co-author of the paper published in the journal The Science of Nature, in a statement. “They are just plain cool. Although people have observed self-assemblages in the past, it's exciting to make new strides in understanding how individuals coordinate to build these structures.”

The ability of many different species of ant to collectively come together and form these rafts during heavy rainstorms, at some moments acting as a solid but in others as a liquid, has intrigued scientists for a long time. A couple of years ago, another study froze ant rafts in liquid nitrogen, super-glued the ants in place, and then CT scanned them to investigate how they hold themselves together. What they found was that when individual ants cling to each other, they do so with all six of their legs as well as their mouth, and tend to grab onto their neighbors' legs. 

In fact, they found that some ants had up to 20 other legs grabbing onto one of theirs. This, they concluded, is what allowed them to move with such flexibility; by bending and stretching their legs, they have greater control over the shape of their overall structure. Another paper has also shown how the ants will protect the most valuable nest mate, namely the queen and her brood, by placing them in the middle of the raft.

This latest study simply adds to the information we already have regarding their ability to self-assemble, showing that they seem to stick to the same role, consistently taking the same place on either the top, middle, base, or side position of the raft. Their research shows the importance of individual differences in behavior when working collectively as a whole, and could impact the development and programming of swarm robotics.