US & Canada

Floating fire ants form rafts in Houston floodwaters

A red fire ant crawls across sand Image copyright Biosecurity Queensland

Whole streets in Texas are underwater, and social media has filled with images of clumps of floating fire ants, massed together in a structure on the surface.

Entomologists say it is normal behaviour after the ants' underground homes get flooded out. In fact it's something they did routinely in the South American floodplains they originated in.

But please do not touch them. They are called fire ants for a reason, because of their burning stings.

"You definitely don't want to get covered in fire ants," says Matt Shadlow, from the UK-based insect conservation society Buglife.

"Steer clear of them."

Red imported fire ants (solenopsis invicta) get agitated and aggressive when disturbed and the first few that sting a person give off pheromone signals to other ants to do the same, so if you get on the wrong side of a colony you could end up with them swarming all over you.

People with allergies to them can also get angry welts or even anaphylactic shock from the stings.

The best tip is to deal with the problem quickly - if you get one on you, pick it off and move away.

So, what about these floating ant clumps that people have been photographing?

Each raft can contain as many as 100,000 individual ants, which use their waxy, water-resistant bodies to link together around their queen as they travel in search of a new place to create the tunnels and chambers that make up their nests.

But the ants on the bottom of the raft have not, as you might think, been sacrificed for the greater good of the queen.

They are still alive. A system of air pockets keeps them able to take in oxygen through the air tubes on their bodies - the same way all insects breathe.

"All insects float," Prof Jim Hardie of the Royal Entomological Society told the BBC.

"The ones at the bottom are properly fine."

They form a sort of material that doesn't even break the surface of the water when pushed down, as seen in this toe-curling YouTube video - it's a material that is now being studied for its engineering properties.

"They've thought of it all, even hurricanes," Prof Hardie said. "They're tough guys."

The ants could survive for weeks without new food sources, eating their young (currently in pupae form) to survive. Once back on dry land they will build a new nest and go back to their normal varied and omnivorous diet, ranging from eggs and other insects to mammal meat, seeds, earthworms and discarded sweets.

People searching for fire ants on Google are also likely to search for how to kill them, it turns out, so here's the lowdown - squeeze some detergent on them, and the surface tension will be broken and they'll drown.

Image copyright Google Trends

Fire ants originally come from South America and were accidentally introduced to the US in the early 20th Century. They also live in Australia, New Zealand, China, Hong Kong, Taiwan and the Philippines. They drive out other species of ant, hurt other animals including livestock and, by building warrens and mounds, can cause structural damage to buildings and pavements.

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