National Geographic : 2012 Nov
NEXT PHOTO: ANAND VARMA. SOURCE: DAVID L. HU AND TIM NOWACK, GEORGIA INSTITUTE OF TECHNOLOGY. ART: SHIZUKA AOKI Survival Rafting When floodwaters strike, the fire ant species Solenopsis invicta reacts with a clever escape plan: Within minutes colony members link their bodies together to form a water-repellent raft that can stay afloat for weeks. Intrigued, Georgia Tech researchers studied in the lab how the insects, native to South America and now roaming the southern United States, interlock claws, mandibles, and sticky pads on their legs to construct the roughly circular rafts. Air bubbles trapped among the ants' bodies and hairs create buoyancy for the two-tiered structure and enable members on its underside to breathe. Colonies of as many as 200,000 ants can form rafts measuring up to two feet wide. And in a remarkable feat of swarm intelligence that helps maintain the raft's integrity, ants on the bottom quickly move on top when others succumb to encounters with debris, predators, or swift currents, says researcher Nathan Mlot. Scientists believe that studying this superorganism could provide new insights into micro-robotics and improved water repellency. ---Patrick Graham 2 1 2 Raft Dynamics By grasping one another with jaws, legs, and sticky pads, fire ants form a raft to ride out floods. The raft's rough and irregular shape increases water repellency. On the raft's underside, air bubbles trapped among the bodies create a pocket that enables the ants to breathe and keeps the structure afloat. 1 When exposed to water, re ants clump together to form a oating ra . Here a ra in its early stages materializes in a laboratory aquarium.