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Ants’ underground cities are architectonic marvels

New research from the California Institute of Technology discusses the remarkable architectonic complexity of anthills, which reach as far as 25 feet underground, are home to millions of ants, and often last for decades. 

By studying the digging habits of ants and uncovering the mechanisms guiding them, scientists hoped not only to increase our understanding of ant cognition and behavior, but also to help improve humans’ ability to dig underground.

“I got inspired by these exhumed ant nests where they pour plastic or molten metal into them and you see these vast tunnel systems that are incredibly impressive,” said Civil and Mechanical Engineering Professor Jose Astrade. “I saw a picture of one of these next to a person and I thought ‘My goodness, what a fantastic structure.’ And I got wondering if ants ‘know’ how to dig.”

Together with Joe Parker, an assistant professor of Biology and Biological Engineering, Andrade devised experiments to study ants’ digging behavior. They started culturing ants and getting them to dig in little soil-filled cups that could be observed through X-ray imaging.

The ants were very efficient, digging the tunnels as straight as possible, and incorporating the cups’ edges into their construction’s structure. “That makes sense because a straight line is the shortest path between two points,” explained Andrade. “And with them taking advantage of the sides of the container, it shows that the ants are very efficient at what they do.”

Ants seemed to have an extraordinary intuitive sense of the laws of physics. They dug their tunnels as steeply as possible, but not so steep that they would collapse. The ants also created subtle rearrangements in the force chains around the tunnels so that the walls were strengthened, but the pressure at the end of the tunnels was relieved, making it easier for them to continue digging. 

But are the ants aware of what they do when they are digging? “What we discovered was that they didn’t seem to ‘know’ what they are doing,” said Andrade. “They didn’t systematically look for soft spots in the sand. Rather, they evolved to dig according to the laws of physics.” 

Humans could not only learn from these remarkable digging methods, but could also devise robotic ants to assist in processes such as mining, underground farming, or subway construction. “This would be the final frontier,” said Andrade.

The study is published in the Proceedings of the National Academy of Sciences.

By Andrei Ionescu, Staff Writer

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