Everything you wanted to know about those horrifying fire ant rafts – Technology & Science

No doubt you’ve seen the horrifying images by now: seething red-brown rafts of up to hundreds of thousands of fire ants matted together, topped by squirming white larvae, floating through the floodwaters and debris left behind by tropical storm Harvey.

And no doubt you have questions: Are all those millions of venomous, stinging ants really all going to survive the flood and move happily back into Texas neighbourhoods afterward? How do they do that? And what should you do if one of them floats by while you’re desperately wading through the floodwaters, trying to get yourself to higher, drier ground?

Here’s what you need to know.

What kind of ants are in those rafts?

They’re known as the red imported fire ant, and their scientific name is Solenopsis invicta. They’re native to South America, and they were first detected in the U.S. in the state of Alabama in the 1930s, according to the Pest Tracker website at Purdue University. They have now spread throughout the southeastern U.S., from Texas to North Carolina. Fortunately, reports of fire ant bites in Canada are relatively rare, and may not be from this species.

Colonies can contain up to 250,000 workers, although most colonies contain only about 80,000.

Are they dangerous?

As its name implies, the ant injects a painful venom when it stings. The imported red fire ant is considered “a human health hazard due to its aggressive behavior and painful sting,” says Purdue University.

Craig Tovey, a Georgia Tech engineering researcher who has studied fire ant raft-building and been stung “more than I’d like” says the ants’ poison is in the same family as black pepper and hemlock, and is “worse than black pepper, but not as bad as hemlock.”

Can the ants swim?

No — that’s what got Tovey and his colleague David Hu interested in fire ant rafts. “Why does a single fire ant Solenopsis invicta struggle in water, whereas a group can float effortlessly for days?” they asked and answered in a 2011 scientific paper published in Proceedings of the National Academy of Sciences.

Individual fire ants struggle in water and will often drown. (David Hu/Georgia Tech)

So how does the raft float?

“It turns out that the ants grip each other and the distance at which they hold each other and the angles at which they hold each other are such that together they form…

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