Images of ants swarming together in ‘rafts’ and riding on top of floodwaters alarm Texans

This article is more than 3 years old

This article is more than 3 years old

There is a new threat to the millions of people in Texas affected by ex-hurricane Harvey: large “rafts” of fire ants that have been spotted floating in floodwaters.

Displaced by record flooding, the insects have responded by creating rafts built on top of other ants to stay on the top of water and keep dry.

Mike Hixenbaugh (@Mike_Hixenbaugh) Pro tip: Don't touch the floating fire ant colonies. They will ruin your day. #Harvey pic.twitter.com/uwJd0rA7qB

Hailing from the floodplains of the Paraguay river in South America, the ants are accustomed to flood-prone environments.

Despite the raft-making behaviour being well known to entomologists (it was observed following hurricane Katrina), images of the ants sailing on floodwaters have caused panic online. A picture of a huge swarm posted to Twitter by Bill O’Zimmerman caused particular alarm.

Bill O'Zimmermann (@The_Reliant) Meanwhile, in Cuero, the river has brought my aunt all of the fire ants. Yes, those are all (of the) fire ants. pic.twitter.com/dEibWYxAdl

Alex Wild, curator of entomology at the University of Texas, said he had never seen anything like the Cuero swarm in his career as an ant researcher.

Fire ants entered the southern United States in the 1930s and have been spreading there with devastating consequences ever since. The ants have also found their way to Australia, China and Taiwan, where they are considered an invasive species. In Australia the ant was first observed in Brisbane in 2001 but has since been spotted in Sydney.

The ants are extremely aggressive, attacking en masse and inflicting an itching and burning sting that can last an hour. Secondary infections from the stings can be serious, and in rare cases allergic reactions have killed people – they are thought to have caused dozens of deaths in the United States.

Compounding the risk posed by the flotillas, the naturally aggressive fire ants are more defensive and deliver higher doses of venom when flooded, according to research by Louisiana etymologist Linda Bui.

Fox Keegan (@FoxCurtailed) If you're in Houston and don't think things could get worse, just remember: Fire Ants float pic.twitter.com/43whwDxnUz

The rafts have been known to last for weeks before breaking up; however without access to food the ants cannot survive.

In the meantime, while some have suggested “killing them with fire” experts say that a bit of detergent is the best defence against the floating menaces.