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How Fire Ants Unite to Survive Floods

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Fire ants floating on a raft made of the ants themselves

We all know how an ant is helpless in water. There’s no surviving the smallest flood for any tiny ant. But in yet another demonstration of the common human wisdom that unity is strength, a colony of fire ants (Solenopsis invicta) whose individual members would otherwise drown if each is alone, can survive a flood by forming a raft and floating away on water for many days.

They do this by holding hands. Well, plus doing other things …

No doubt certain biological features of the fire ant make it easier for them to form a floating vessel using their own bodies; but this takes little away from the excellence exhibited by these social insects in this feat.

One study published in the Journal of Insect Science, (conducted by researchers Benjamin J. Adams, Linda M. Hooper-Bùi, Rachel M. Strecker and Daniel M. O’ Brien) made some interesting findings which imply that the ants also consciously engage in other behavior which makes the formation of the raft possible during a flood.

For instance among fire ants, the setae (the ‘hair’ found on insects) of their young larvae is hydrophobic. It kind of repels water and tends to trap a lot of bubbles when submerged. These bubbles are instrumental to the buoyancy of the ant colony’s raft and how long the ants can survive floating. For this reason, fire ants intelligently place their larvae under the raft and use them as a foundation.

But wait. Even on their own, when fire ants find themselves submerged in water, they do the amazing. They calmly roam just like they do when looking for food on land, collecting bubbles from here and there on objects at the bottom of the water and adding them to other tiny bubbles trapped by their own setae and other body parts. In doing so, when a fire ant gets a bubble that is huge enough, it’s able to use the bubble to float to the surface and join its colleagues! This specific behaviour of using bubbles to rise to the surface of water was previously unheard of among social insects.

Fire ant with bubbles (Image: Ant Laboratory, Georgia Institute of Technology)

Another thing fire ants do is to rotate, rotate and rotate. By marking the ants’ positions before they formed the raft and identifying which ones actively connected their bodies to form the raft and which ones were moving freely on the upper levels after forming the raft, the researchers found that there is constant cycling of roles and positions between the ants who do the hard work of interconnecting their bodies to form the raft and those who are free to walk about on the top doing other things.

Effectively, this ensures that ants at the bottom of the raft that may find themselves enduring higher levels of stress and contact with the water, do not stay there for too long.

Unsurprisingly, fire ants are an invasive species who know how to break boundaries and establish themselves in other territories. Key to that is their ability to gather and connect themselves within minutes and float away during floods. And at the heart of this ability is the knowledge that there is strength in unity.

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