Army ants in Central and South America aggressively seek out the shortest path over the forest floor to bring home enough food and ensure the future of their colony. This focus on efficiency led the insects to develop a clever trick: They link their bodies together to fill potholes and build living bridges.
As more ants join in, the bridges shift locations to span larger and larger gaps, shortening the path ants have to take when carrying food back to the nest. But because each brick in the bridge is also a lost forager, the ants reach a point where a slightly better shortcut just isn’t worth the cost, according to new analysis of this insect construction work.
“Overall, that cost-benefit tradeoff is reached, but without any ants really knowing,” says study leader Chris Reid of the University of Sydney.
Reid’s study, appearing this week in PNAS, is the closest look yet at the architectural algorithms army ants use when they build bridges. Understanding these rules could help scientists design smarter robotic swarms, for instance, by programming self-assembling materials to create dynamic structures as big as life rafts or as small as surgical stents.
To see their subjects ant-scaping in the wild, Reid’s team headed into the jungle of Panama’s Barro Colorado Island. Army ants from the genus Eciton, though voracious little murderers, are prudent when it comes to sustainable hunting. After a hard day pillaging larvae from the colonies of other ants and wasps, they pick up and march to new territory a few hundred feet away.
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