‘Safety nets’ built by army ants could help engineers design self-healing robot flocks

Teamwork is not just a human trait: Colonies of army ants will form living ‘scaffolds’ to protect members from falling.

The insects are blind and do not have a designated leader but, according to new research, they can use simple rules of conduct to develop these safety structures without the need for direct communication.

After scaffolding was built, workers’ ants were almost 100 percent protected from falling off steep slopes.

Understanding how they design such complex structures could help engineers develop self-healing materials and flock robotics, researchers say.

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Army ants in the Central American rainforests will build scaffolding out of their body to help them cross steep terrain.  The 'safety net' maintains its structure even across almost vertical slopes

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

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

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

Researchers have discovered a new type of ‘army ant architecture’, living scaffolding that prevents ants carrying prey to the colony from slipping and falling if the path becomes too steep.

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

The scientists redirected the colony's search trail to a platform they could draw up to 90 degrees horizontally

The scientists redirected the colony’s search trail to a platform they could draw up to 90 degrees horizontally

The scientists redirected the colonies’ search routes to a platform that they could draw up to 90 degrees horizontally, and observed the creation of this scaffold.

There seemed to be a sweet spot: Nothing below 40 degrees was likely to cause a scaffold to form, according to their report this week in the Proceedings of the National Academy of Sciences of the USA.

Much steeper trends ‘led to larger structures and faster growth,’ according to a statement.

‘Scaffolding is also more likely to form when many workers carry heavy prey items,’ said biologist Matthew Lutz, the study’s lead co-author.

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

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

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

‘It’s amazing how quickly these structures form in response to disturbance when crossing slopes,’ Lutzsaid.

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

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

Millions of workers are constantly searching for food, eating up to 500,000 larvae, eggs and other delicious morsels every day.

Each ant is only a quarter to a half inch in size but a colony search route can be more than 325 feet long and 60 feet wide.

Scientists do not quite understand how the ants form these super-scaffolds: They are practically blind and, although they have a queen, have no central authority when moving as a unit

Scientists do not quite understand how the ants form these super-scaffolds: They are practically blind and, although they have a queen, have no central authority when moving as a unit

Scientists do not quite understand how they form these superstructures: Although they have a queen, there is no central authority when it comes to moving as a unit.

In addition, army ants are almost blind and rely on pheromone to communicate.

The researchers – which included experts from the Max Planck Institute for Animal Behavior in Konstanz, Germany; Macquarie University in Sydney, Australia; New Jersey Institute of Technology; and the Santa Fe Foundation in New Mexico – the ants can theoretically sense how much they slip and form these scaffolds spontaneously when they lose their grip.

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

Army ant is the largest species of ant on Earth, and every queen has the capacity to lay several million eggs each 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 Macquarie University researcher.

‘Army ants are small, blind and do not have leaders or blueprints to direct them, yet their ability to produce sophisticated behavior at a group level of simple rules at a local level is invaluable to many engineering fields, including flock robotics. ‘

Cracking the code on how they produce these structures with little input or knowledge would boost robotics, architecture, and engineering.

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

Other ants create structures as well: Colonies of fire ants form ‘rafts’ to ride floods to safety.

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