Structure of fire ant rafts studied with 3D scanners

Nature : Fire ants are known to clump together into “rafts” that let them cross rivers. David Hu of the Georgia Institute of Technology in Atlanta and his colleagues wanted to understand the structures that the ants formed. To do that, they collected ant colonies, let the ants form balls that they froze with liquid nitrogen and then sprayed with vaporized glue to hold the ants in place. They then created a digital map of the structure using a micro-computed-tomography scanner. The map revealed that the ants held onto each other using adhesive pads on their legs and tended to arrange themselves perpendicular to each other. The structure also seemed to efficiently use the ants’ differing sizes, like different size panels on a soccer ball. Each ant averaged 14 points of connection with other ants in the structure. Hu’s group is now working to examine other ant structures.