July 18, 2024

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The study concluded that fire ant rafts are formed due to the Cheerios effect

The study concluded that fire ant rafts are formed due to the Cheerios effect
Zoom / Georgia Tech scientists have found that the so-called “Cherios effect” is the mechanism by which fire ants huddle together to form rafts.

Hangtang Koh

Fire ants may be a scourge of southern states like Georgia and Texas, but scientifically they are Fantastic to infinity An example of group behavior. A few well-spaced fire ants behave like individual ants. But pack enough of them together closely, and they’ll work more like a single unit, exhibiting solid and liquid properties. They can form rafts to survive flash floods, arrange themselves in towers, and you can even pour them from a teapot like liquids.

“Combined, which can be considered as a substance, is known as the ‘active substance,'” he said. Hangtang Koh, now a postdoctoral researcher at Princeton University, who began studying these adorable creatures when he was a graduate student at Georgia Tech in 2018. (And yes, he was stung many times.) Fire ant pontoons. the first, Posted in The journal Bioinspiration and Biomimetics (B&B) investigated how fire ant rafts behave in flowing water compared to still-water conditions.

Second, accepted for publication In Fluids of Physical Review, explore the mechanism by which fire ants come together to form rafts in the first place. ko and others. They were somewhat surprised when they discovered that the initial mechanism looked as if itCheerios effectIt was named in honor of the tendency of the last remaining Cheerios floating in milk to clump together in the bowl, either by drifting to the center or to the outer edges.

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One ant has a certain amount of hydrophobia, that is, the ability to repel water. this is Property has been condensed When bonded together, they weave their bodies like a waterproof fabric. The ants collect any eggs, make their way to the surface through their nest tunnels, and as the flood waters rise, the ants nibble on each other’s bodies with their lower jaws and claws until a flat raft-like structure forms. Each ant behaves like a single molecule in a substance, for example, grains of sand in a sand pile. Ants can achieve this in less than 100 seconds. In addition, the ant raft is “self-healing”: it is strong enough that if an ant is lost here and there, the overall structure can remain stable and intact, even for months at a time.

In 2019, Ko and colleagues This has been reported Fire ants can actively sense the changes in the forces acting on their floating raft. The ants are aware of different fluid flow conditions and can adapt their behavior accordingly to keep the raft stable. An oar moving through the river water will create a series of whirlpools (known as a shedding vortex), causing the ants’ rafts to spin. These vortices can also exert additional forces on the raft, enough to break it apart. The changes in both the centrifugal forces and the shear forces acting on the raft are very small – perhaps 2 percent to 3 percent of the normal gravitational force. However, somehow, ants can feel these small shifts with their bodies.

Earlier this year, researchers at the University of Colorado, Boulder, I set some simple rules Which appears to control how floating fire ant rafts shrink and expand their shape over time. as such inform us At that time, structures were sometimes compressed into dense circles of ants. Other times, the ants will begin to spread out to form bridge-like extensions (pseudopods), sometimes using the extensions to escape from the containers.

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How did the ants achieve these changes? The pontoons mainly consist of two distinct layers. The ants in the bottom layer serve a structural purpose, as they form the stable base of the raft. But the ants in the upper layer move freely over the bodies attached to their brethren in the lower layer. Sometimes ants move from the bottom layer to the top layer or from the top layer to the bottom layer in a vicious cycle.

ko et al.The B&B study is somewhat related to focus, with the exception of the Boulder study which looked at broad collective dynamics rather than interactions between individual ants. “There are thousands and thousands of ants in the wild, but nobody really knows how a pair of ants will interact with each other, and how that affects the stability of the raft,” Koe told Ars.

With such large rafts, redundancy can be an issue. Koe wanted to gain more control over his experiments and also study how the ants adapted to different flow scenarios in the water. He found that the ants use an active simplification strategy, changing the shape of the raft to reduce drag. “So it probably takes less force, or less metabolic cost, to stick to the plants than if they had stuck to the original, larger pie shape,” Koe said.