How do fire ants present together in large numbers float on water?
A single fire ant (Solenopsis invicta) dropped in water struggles, but when there are many of them together, the ants can float effortlessly even for days at a stretch. Fire ants are originally from the rainforests of Brazil and have evolved a strategy to keep their colonies together due to the regular flooding of their habitat. Using time-lapse photography, a three-member team led by David L. Hua from Georgia Institute of Technology, Atlanta, U.S. found that fire ants, when present in a group, tend to link their bodies together to build “waterproof rafts.” Lotus leaves, rose petals and a host of other plant parts exhibit water repellency. Water repellency is achieved through the hydrophobic nature of the surface. Much like lotus leaves, the researchers found that the fire ants that gathered together in water exhibited a hydrophobic surface. By linking their bodies together, a process analogous to the weaving of a waterproof fabric, the fire ants enhanced their water repellency, they write in a study published in the journal Proceedings of the National Academy of Sciences. The waterproof raft they build, by linking their bodies, is achieved by trapping of ants at the raft edge by their neighbours. The researchers used liquid nitrogen to freeze the ants to study how the ant linked together within the raft. They found that ants, “gripped each other by using a combination of mandibles, tarsal claws, and adhesive pads located on the ends of their tarsi,” (the bones of the proximal segment of the foot).
