Those living in fire ant territory have likely seen a peculiar sight: after a storm, massive clumps of ants will form on the top of large puddles and flooded areas. Researchers have known about this phenomenon for years, but until now, no one knew just how the ants managed to pull off that feat.
Buoyant larvae, it turns out, are the secret to the colony's success at surviving floods. As National Geographic reports, ants "work together to protect the queen by strategically placing larvae, pupae, and worker ants at the bottom of the raft." It's the youngest members of the colony, the larvae, that make up the very bottom of the pile. After the workers grab the nearest larvae and throw them under the heap, they then "link jaws to limbs and move around to give the raft its structure," the Los Angeles Times says. The queen is placed in a position of honor at the very center of the raft—the stablest and safest location for sitting out the flood.
The larvae are better built for floating than the workers, likely because of their higher fat content, the researchers report. They discovered that even though those delicate babies risk getting picked off by fish or swept away by currents, in the end, fewer lives are lost than if worker ants assumed that bottom-of-the-pile role. "Without larvae and pupae under the raft, 25 to 50 percent of the worker ants had at least partial contact with the water, putting more of them in danger," NatGeo writes of the results. The larvae, the Los Angeles Times adds, seemed to suffer "no long-term ill effects from being put to work like this," as they grew up normally after recovering from the traumatic event.
The authors of the study used a species of ant called flood ants in their analysis, but say that the same strategies would likely hold true for other ants, including those notorious fire ants.
Here, you can see an ant raft in action, courtesy the BBC: