The Physics of Creepy-Crawly Fire Ant Rafts Could Help Engineers Design Swarming Robots

Fire ants survive floods by forming rafts made up of thousands of wriggling insects. A new study by engineers at CU Boulder lays out the simple physics-based rules that govern how these ant rafts morph over time: shrinking, expanding or growing long protrusions like an elephant’s trunk. Fire ants form these giant floating blobs of wriggling insects after storms in the southeastern United States to survive raging waters.

The group reported that the ants seemed to modulate these shape changes through a process of “treadmilling.” Every ant raft is made up of two layers. On the bottom, you can find “structural” ants who cling tight to each other and make up the base. Above them are a second layer of ants who walk around freely on top of their fellow colony-members. Over a period of hours, ants from the bottom may crawl up to the top, while free-roaming ants will drop down to become part of the structural layer.

“Our work on fire ants will, hopefully, help us understand how simple rules can be programmed, such as through algorithms dictating how robots interact with others, to achieve a well-targeted and intelligent swarm response,” lead author Robert Wagner said. The team’s findings could one day help researchers design robots that work together in swarms or next-generation materials in which molecules migrate to fix damaged spots.

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