18 May 2011
Posted in NatureWorks
In a recent study, scientists from the Georgia Institute of Technology in Atlanta found that fire ants form seals so tight that not even water can get through. The researchers say it’s as though the bugs are weaving a waterproof fabric out of themselves. The ants on the bottom don’t drown, and the ants on the top stay dry. Working together, the ants float to safety — even though a single ant alone in the water will struggle to survive.
Fire ants are famous for their construction projects (as well as their burning bites). When they need to, colonies of these insects turn themselves into ladders, chains and walls. And when floodwaters rise, a colony can float to safety by making an unusual boat. The ants hold tightly to each other, forming a buoyant disk atop the water. The ant-raft may float for months seeking safe harbor.
Fire ants and water don’t mix. The ant’s exoskeleton, or hard outer shell, naturally repels water. A drop of water can sit on top of the ant like a backpack. When an ant does end up underwater, tiny hairs on its body can trap bubbles of air that give the bug a buoyancy boost.
But that’s just one ant. No matter how well it repels water, a single ant doesn’t explain how a whole colony stays afloat. To investigate the science behind the ant-raft, the Georgia Tech researchers went out and collected thousands of fire ants. The species the researchers collected was Solenopsis invicta, which is better known as the red imported fire ant, or RIFA.
The scientists placed hundreds or thousands of ants at a time in the water. A group of ants took about 100 seconds, on average, to build a raft. The researchers repeated the experiment multiple times. Each time, the ants organized themselves the same way, creating a raft about the size and thickness of a thin pancake. (The more ants, the broader the pancake.) The rafts were flexible and strong, staying together even when the researchers pushed the rafts underwater.
The scientists then froze the rafts in liquid nitrogen and studied them under powerful microscopes to figure out how the ants kept everyone safe and the water out.
The team found that some ants used their mandibles, or jaws, to bite other ants’ legs. Other ants joined their legs together. Thanks to these tight bonds, say the scientists, the ants did a better job at keeping the water away than any one ant could do on its own. By working together, thousands of ants can stay alive in the face of a crisis like a flood by using their own bodies to build a boat.