The flimsy arms of the teeny tiny fire ant are the building block for some surprisingly sturdy bridges.
Fire ants are extraordinarily resilient for their tiny size. They can survive fires, they carry potentially-deadly toxic venom, and they can strip small rodents down to a skeleton. They even build bridges with their bodies by locking limbs to cross gaps.
The fire ant is so resilient that it’s quickly become a dangerous invasive species in the U.S. after hitching a ride aboard a trade ship back in the 1930s. The tiny invaders’ bites cause lots of medical expenses and agricultural damage every year.
Most fire ants only weigh a fraction of a gram so it seems like a bridge made of these tiny insects would blow over in the slightest breeze or fall apart with a gentle bump.
But fire ants are native to Brazil, where they face periodic floods. The ants have evolved the ability to band together and build bridges and rafts with their bodies to escape flood waters and make it to dry land. They can build floating rafts across water:
And build bridges to keep dry:
These bridges are often seen hanging between leaves or reeds as whooshing winds and raging waters shake the plants and threaten to destroy them. How do these tiny ants do it?
David Hu and Sulisay Phonkeo from the Georgia Institute of Technology tested how these bridges are able to stand up to intense vibrations in the lab and reported their findings at the Society for Integrative and Comparative Biology meeting.
You can see how flimsy the bridge from their experiment looks in the GIF below. Vibrations in the two pipes had already started, and the connection seems to be on the verge of collapsing.
The researchers suggest that the ants can sense if they are in areas of the bridge that’s weakening and tighten their limbs and stick closer together to solidify the arch. This extra tension from hundreds of teeny tiny ant limbs shortens the arch of the bridge, making it stronger and more rigid.
Ants attempting to cross as the bridge weakens also react — they scramble back to the ends of the bridge to put less weight on the more vulnerable center.
You can see that the arch in the bridge gets smaller and the ants clasp together tighter as they lock their limbs and pull together.
Business Insider Emails & Alerts
Site highlights each day to your inbox.