Team building: A study on the behaviour of Ants

A team of engineers has discovered how colonies of ants survive floods by forming themselves into life rafts. The work shows how many simple components can interact to create complex structures and behaviours, a subject that touches on crowd control, urbanization and robotics.

An individual ant can float on water for a few minutes, but a clump of the insects is heavy enough to break the surface tension of the water and sink. Yet when a nest of fire ants (Solenopsis invicta) is flooded, the entire thousands-strong colony shapes itself into a raft that can stay afloat for months.

"Together they form this really complex material that water should be able to get through, but can't," says Nathan Mlot, a mechanical engineer at Georgia Institute of Technology in Atlanta. Mlot and his colleagues have shown how these rafts are built and why they float. Their findings are published this week in Proceedings of the National Academy of Sciences¹.

When Mlot put thousands of ants in an empty beaker and swirled it, the insects clung to each other, gripping tightly to form a sphere that felt like a squashy ball, he says. Wearing gloves to avoid being bitten, Mlot could toss the clump in the air and catch it without any ants falling off.

When such a sphere is placed in water, it relaxes into a dome and, within minutes, flattens into a pancake.
The ants that hit the water first hook together with their jaws and legs, forming a tightly woven base. As the dome flattens and more ants reach the edge of the mass, their comrades at the bottom grip them tightly, weaving them into the base to help support the rest of the colony. At its flattest, the raft consists of two to three levels of ants, with the upper levels milling around on their interwoven nest mates.

A lone ant's exoskeleton can trap air bubbles and become slightly water repellent, but the surface of an interwoven group does so much more effectively, keeping the ants dryer.

Although the raft is porous and its base is below the water level, none of the ants are submerged, or even get wet. Instead, the ants at the base of the raft push against the water's surface and shape it around them into a bowl without breaking the surface tension.

Lizzie Buchen in Nature. More Here

Ants and humanbeings

It is easy to imagine that the lives of the ants resemble our own. An ant might feel, as people sometimes do, lost in the crowd. If you look at a city from far away, you see a hive of activity: people going back and forth from home to job and collecting packages of food and things produced by other people, things to be stored in their chambers or turned into garbage taken away by other people. Each person is a tiny speck in the flow of a system that no one has much power to change.

Our fascination with ants has led to engaging stories about them, from the Iliad’s Myrmidons to Antz’s Z, as well as a growing body of research by biologists. Though the ant colonies of fable and film often are invested with the hierarchical organization characteristic of human societies, a real ant colony operates without direction or management. New research is showing us how ant colonies get things done without anyone being in charge. Ants, it turns out, have much to teach us about the decentralized networks that operate in many biological systems, in which local interactions produce global behavior, without the guidance of any central intelligence or authority.


Understanding how ant colonies actually function means that we have to abandon explanations based on central control. This takes us into difficult and unfamiliar terrain. We are deeply attached to the idea that any system of interacting agents must be organized through hierarchy. Our metaphors for describing the behavior of such systems are permeated with notions of a chain of command. For example, we explain what our bodies do by talking about genes as “blueprints,” unvarying instructions passed from an architect to a builder. But we know that instructions from genes constantly change, as genes turn off and on in response to local interactions among cells.

Ant colonies, like genes, work without blueprints or programming. No ant understands what needs to be done or what its actions mean for the welfare of the colony. An ant colony has no teams of workers dedicated to fighting or foraging. Although it is still commonly believed that each ant is assigned a task for life, ant biologists now know that ants move from one task to another. How does an ant decide which task to do and when to do it? We all know that where there is a picnic, there will be ants. So what determines which ants go to the picnic, and how many show up?

But though we humans can be in some ways ant-like, ants are not like us. It takes a work of fiction to give ants identity, feelings, and motives that we recognize as human. For ants, only the structure of the network matters. For us, the content is crucial. We care about what the emails say; the ants care only about how often they get them. As we move through the networks that shape our lives, we constantly produce a narrative about what is happening and why. We may be wrong about what we think is going on, but it is vitally important that we think we know.

Our stories about ants always have morals about how people ought to behave: soldiers should die for their country; we should conserve resources and plan for the future; a dutiful factory worker should cheerfully perform his or her appointed task. These morals come from stories about ants that are not true.
Real ants do not offer lessons in behavior. They do, however, provide insight about the dynamics of networks. Ants can show us how the rhythm of local interactions creates patterns in the behavior and development of large groups. There are no morals to be taken from the ants, but there is much to learn about systems without central control.

Deborah M Gordon in Boston Review. More Here.