Fire ants floating on water in a ‘raft’
Ants have exoskeletons that are naturally hydrophobic, or water repellant. A single ant can walk on water because of the buoyancy of the air bubbles trapped next to its body, and the water’s own surface tension. However, when thousands of ants stand on top of each other, their multiplied weight should cause them to sink. But for years, biologists have observed fire ant colonies floating down flood plains and rivers in their native South America.
Ants float as a group because they can harness the power of nearby air bubbles. Grasping each other’s mandibles or front legs with a force 400 times their body weight, the ants are able to trap small pockets of air between them — like a group floatation device.
The bottom layer of ants rests on top of the water’s surface, and others pile on above them. Even when they do get submerged, the pockets of air bring them back to the surface quickly — and allow them to breathe. When they get submerged, the ants flex their muscles in unison to form a tighter weave.
In the top gif if you look at where the water meets the side of the tank you’ll be able to see the meniscus (skin) of the water stretching as the ants are forced down.
gif sources 1, 2