Researchers at the Georgia Institute of Technology, United States, have discovered that fire ants ( Solenopsis invicta ) create a kind of waterproof raft when there are floods to save the colony. It is a tortilla-shaped structure, and almost half of the colony is submerged to keep the rest afloat, as explained in an article published today in the journal Proceedings of the National Academy of Science (PNAS).
To see how these highly invasive insects react to an emergency by collaborating with each other , the team led by David Hu threw between 500 and 8000 ants into the water. They observed that they clumped together rapidly, grasping each other with their jaws and forceps to form the structure. Trapped air formations under the rafts likely increase buoyancy and prevent bottom layer ants from drowning, the authors note. By gradually removing the ants from the top, they verified that those at the bottom were moving to preserve the average thickness of the reservoir. According to the researchers, this cooperative behavior among fire ants could be based on coercion.
Although S. invicta is native to South America, the ant has become a pest in the southern United States, Australia, the Philippines, Taiwan, and southern China's Guangdong province.
