Floating fi re ants another woe for hurricane victims

In addition to widespread suffering and devastation, Hurricane Harvey has brought a plague of floating fire ants to the Houston region.

“Floodwaters will not drown fire ants,” wrote Paul Nester, an extension specialist at Texas A&M, in a pamphlet titled “Flooding and Fire Ants: Protecting Yourself and Your Family.” Instead, entire colonies of the aggressive biting insects — eggs, larvae and all — will “emerge from the soil, form a loose ball, float, and flow with the water until they reach a dry area or object they can crawl up on.”

Fire ants are aggressive, territorial and venomous. Among vulnerable individuals, their stings can be fatal. “Most people hate fire ants without reservation,” Florida State University entomologist Walter Tschinkel wrote in a book about the insects in 2006.

People in areas around Houston reportedly are seeing dozens of colonies come ashore in the wake of the flooding there.

Researchers have extensively studied the floating behavior. A 2011 paper by David Hu and colleagues at Georgia Tech found that when a clump of fire ants are dropped on a surface of water, they will cling to each other and distribute themselves into a pancake-shaped disc.

The ants can do this because their bodies partially repel water, or, in scientific terms, they are “hydrophobic.” When water comes in contact with a fire ant, it beads up into droplets.

“An advantage of being hydrophobic is the ability of ants and semiaquatic insects to trap a plastron layer of air around their bodies, without which they would sink,” Hu and his colleagues wrote.

The trapped air bubbles around the ants make a flotilla particularly hard to sink, and it allows a colony of fire ants to survive on the water for weeks.

But that doesn’t mean they’re invincible. In fact, they have an Achilles’ heel: dish soap.

Spray a bit of soapy water on an ant raft and it will break apart and begin sinking almost instantaneously. “As soon as ants become even slightly soapy, they immediately release their grip with each other, which is shown by the disintegration of the raft and its submergence underwater,” Hu and his colleagues found.