Army ants build 'safety nets' to catch falling comrades

‘Safety nets’ built by army ants to catch falling comrades could help engineers design self-healing robot swarms

  • The living ‘safety net’ is almost 100 percent effective, according to researchers
  • The scaffolds stayed intact even across completely vertical slopes
  • The ants  develop the structures despite being blind and having no leader
  • Understanding how they do it could help engineers development adaptive robot swarms 

 Teamwork isn’t just a human characteristic: Colonies of army ants will form living ‘scaffolding’ to protect members from falling.

The insects are blind and have no designated leader but, according to new research, they’re able to use simple behavioral rules to develop these safety structures without the need for direct communication.

Once a scaffold was built, worker ants were almost 100 percent protected from falling off steep inclines. 

Understanding how they design such complex structures could help engineers development self-healing materials and swarm robotics, researchers said.

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Army ants in Central American rainforests will build scaffolds out of their body to help them traverse steep terrain. The ‘safety net’ maintains its structure even across virtually vertical slopes 

There are over 200 different species of army ants (Eciton burchellii), mostly found in the rainforests of Central and South America. 

To traverse the treacherous forest floor, worker ants form ‘highways’ and ‘bridges’ with their bodies.

Researchers have discovered a new kind of army ant ‘architecture,’ a living scaffolding that prevents ants carrying prey for the colony from slipping and falling if the trail gets too steep.

An international team of entomologists studied the structures created by colonies of army ants in Panama.

The scientists redirected the colony’s foraging trail onto a platform they could tip up to 90 degrees horizontally

The scientists redirected the colonies foraging trails onto a platform they could tip up to 90 degrees horizontally, and observed the creation of this scaffold.

There appeared to be a sweet spot: Anything under 40 degrees wasn’t likely to cause a scaffold to form, according to their report this week in Proceedings of the National Academy of Sciences of the USA.

Much steeper inclines ‘led to larger and faster-growing structures,’ according to a release.

‘Scaffolds are also more likely to form when many workers are transporting heavy prey items,’ said biologist Matthew Lutz, co-lead author of the study.

Virtually no ants fell once a scaffold was in place, even across vertical surfaces.

Anything under a 40 degree slant was unlikely to cause a scaffold to form. The steeper the slope, the faster and larger the structure

‘It’s remarkable how rapidly these structures form in response to disruption when crossing slopes,’ Lutzsaid.

‘They are really a form of self-healing, responsive infrastructure.’

Army ants are the largest on Earth, and each queen has the capacity to lay several million eggs every month.   

Millions of workers forage for food constantly, consuming up to 500,000 larvae, eggs and other tasty morsels every day.

Each ant is only a quarter to a half-inch in size but a colony’s foraging trail can be more than 325 feet long and 60 feet wide.

Scientists still don’t fully understand how the ants form these super-scaffolds: They’re practically blind and, while they have a queen, there is no central authority when it comes to moving as a unit

Scientists still don’t fully understand how they form these super-structures: While they have a queen, there is no central authority when it comes to moving as a unit.

In addition, army ants are virtually blind and rely on pheromones to communicate.

The researchers — who included experts from the Max Planck Institute of Animal Behavior in Konstanz, Germany; Macquarie University in Sydney, Australia; the New Jersey Institute of Technology; and the Santa Fe Institute in New Mexico — theorized the ants can sense how much they’re slipping and spontaneously form these scaffolds when they’re losing their grip.

Army ants are the largest species of ant on Earth, and each queen has the capacity to lay several million eggs every month

‘Our model closely matches the experimental results, without requiring the ants to communicate with each other or assess the size of the structure,’ said co-lead author Chris Reid, a researcher at Macquarie University.

‘Army ants are small, blind and have no leaders or blueprints to direct them, yet their ability to generate sophisticated group-level behavior from simple local-level rules is extremely valuable to many engineering fields, including swarm robotics.’

Cracking the code on how they generate these structures with little input or information would be a boon to robotics, architecture and engineering.

A swarm of miniature robots could potentially be sent to a disaster site and form a necessary structure to help with recovery, regardless of whether it was ‘programmed’ into their network beforehand, the authors wrote in The Conversation.

Other ants create structures, too: Colonies of fire ants will form ‘rafts’ to ride out a flood to safety.

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