As the ants, which have a coating on their armorlike bodies that repels water, drifted in teeming clumps, their presence formed a “creepy” subtext to the tales of woe and rescue in Houston’s flood-drowned streets, creating a “river full of nightmares,” The Houston Chronicle wrote.
Mike Hixenbaugh, a medical writer for The Chronicle, recorded a video of one such fire ant cluster while working on a flood story on Monday in Cypress Creek. He said in an email that later that day he stepped on another group of fire ants that “tore my left ankle/foot up.”
“Those bites itch for days,” he said.
Online, the video inspired stories about the ants in Wired, The Verge and elsewhere.
On Twitter, people shared stories of run-ins with the tiny creatures.
“Had a golf ball size group wash up on my foot during flooding near Austin,” one wrote, adding that he “screamed” and “ran home to a fistful of Benadryl.”
“I haven’t read the Bible but, from what I’ve heard, this seems like ‘the stuff of Revelations,’” wrote another person in reply to one of Mr. Hixenbaugh’s tweets.
Fire ants are native to South America and adapted to surviving in flood plains in the wetlands of Brazil. In the United States they are concentrated mostly in the southeastern region, with smaller populations in New Mexico, Arizona and California.
If disturbed, they become aggressive and bite, attaching to humans with their jaws, and injecting a stinging venom that burns and develops into fluid-filled pustules. First aid, according to the Centers for Disease Control and Prevention, includes use of an epinephrine pen or antihistamines. Allergies to insect bites can be deadly.
Scientists have studied the ants for their unusual ability to band together. In July, Vox made a video of the ants, showing how they stuck so well that they could be ladled en masse for easy transference from surface to surface. When their cluster is poked with a finger, it bounces back.
If subjected to longer periods of disturbance, the ant cluster acts like a fluid. When a coin is dropped into an aggregation of the insects, the group reforms slowly around the object. Scientists at Georgia Tech have been studying the physics and behavior of fire ant clusters, which have a consistency they say can be wobbly like Jell-O or flow like ketchup.
They do this by connecting with their legs — 100 ants means 600 legs — creating a springy network that repels liquid because of a coating on their bodies. “They weave into a waterproof fabric,” said David Hu, who is studying fire ants at Georgia Tech.
They live in organized societies called colonies, which can have tens of thousands of members, reproducing and collecting food. They are led by a queen — the only member that reproduces, said Lawrence Gilbert, the director of the Invasive Species laboratory at University of Texas at Austin.
Fire ants are no stranger to the surface during tropical storms and hurricanes. If water seeps into their tunnels — some of which can stretch four feet deep — they try to escape with their larvae, pupae and food.
“Imagine yourself as an ant in a mine with vertical tunnels,” Dr. Gilbert said. “And now you are just picking up your babies and running uphill. They move up en masse to the top, just like people on roofs.”
Those at the bottom of the pile eventually change places with those at the top, and the mass endlessly revolves around the colony’s offspring and queen. “They are probably moving around enough so they are not drowning,” he said.
They can drift for days, until they find a log or a bank. If one colony bumps up against another, they fight for territory.
They can be aggressive, and sneaky. Dr. Gilbert said fire ants would crawl up the pant leg of an unsuspecting person standing on top of their mound. “You won’t feel anything for a minute,” he said. “What they are doing is mustering.”
They are looking for hair to attach to, he said.
“You might feel tickling, and then suddenly they are latching on so they can drag that stinger in,” he said. “Once one of them stings it lets off a pheromone, and that makes everybody sting at once. It is like you are stepping into fire.”
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