When red fire ants hear rain drumming on the ground they quickly evacuate and create a "living raft."
The ants create these rafts by gripping onto each other; the likelihood of one ant sinking is much greater than an entire mass, a Company of Biologists news release reported.
These ants have also been known to create bivouacs, towers, and even droplets.
"You can consider them as both a fluid and a solid," David Hu from the Georgia Institute of Technology said in the news release.
The researchers swirled 110 ants in a beaker so that they formed a sphere, the team then froze that sphere in liquid nitrogen and Super GlueTM vapor. They looked at the inner working of the structure using a CT scan, allowing them to see every detail.
"With the CT scan we can focus on individual ants and see how they are connected to their [neighbors],"Hu said.
After analyzing the structure for several months the researchers determined that each ant took part in 14 contacts. The ants reached out with each of their six legs to grab onto their neighbors and also could have eight others attached to their bodies; larger ants could reach up to 20 contacts, smaller ones could only have about eight.
"It turns out that 99 [percent] of the legs are connected to another ant and there are no free loaders," Hu said.
Instead of "clustering together in parallel" the ants angled their bodies perpendicular to each other.
"They have to be alive to do that," Hu said. "It requires some intelligence, and suggests that somehow they sense their relative orientation."
The team also looked at how closely the ants packed their bodies together; they found smaller ants were "packed in" to fill the gaps between the larger ones, actively pushing in on each other.
"So, having discovered how fire ants self-assemble to form light but stable structures, Hu is keen to know how they react to reinforce weak points in structures where ant architecture could fail," the news release reported.
