Floating Fire Ants Mess with Texas


They’re more venomous, more aggressive, and “Holy crap. I have never, in my entire career as an ant researcher, seen *anything* like this.” (The Atlantic)

What are fire ants?

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Red imported fire ants (RIFA) can survive up to a month in floating, entirely waterproof colonies like this one.
Photograph by TheCoz, courtesy Wikimedia. CC-BY-SA-4.0

Discussion Ideas


These photos show the water repellency of fire ant rafts. (A) An individual ant’s exoskeleton is moderately hydrophobic. (B) The enhanced water repellency of a raft is shown by the increased contact angle of the water drop. (C) Buoyancy and elasticity of the ant raft are shown by attempted submersion by a twig. (D) An air bubble makes the ant buoyant, necessitating the use of a thread to hold it underwater. (E) An air pocket is trapped in a submerged ant raft.
Photographs courtesy Nathan J. Mlot, Craig A. Tovey, and David L. Hu. “Fire ants self-assemble into waterproof rafts to survive floods” PNAS 2011 108: 7669-7673
Fire ants clump together in mandible-tarsus and tarsus-tarsus connections. (An ant’s mandible is its mouthparts, and its tarsi are the five segments of its legs.)
Illustration by Shizuka Aoki, National Geographic
  • Why are floating fire ant colonies more dangerous than terrestrial ant colonies?
    • Floating fire ants “deliver higher doses of venom because they have 165 percent as much venom inside them as normal fire ants. The flooding [makes] them more aggressive and dangerous.”
    • The colonies can also be well-hidden. “Piles of debris can act like islands, where fire ants have congregated during the flood.”
    • “After Hurricane Katrina, Linda Bui, an entomologist at Louisiana State University, remembers seeing evacuees from New Orleans come into a field hospital with bands of unexplained rashes around their legs and waists after wading through floodwaters. ‘They were like something none of the medical professionals had ever seen,’ she says. ‘I was like, ‘Those are literally fire ant stings on top of fire ant stings.’”


  • How do rescue workers, pest control officers, and everyday citizens fight fire ants?
    • wait. The ants will drown if floodwaters persist, as happened after Hurricane Katrina.
    • insecticide. Pest control agents often inject insecticide in fire ant mounds or insert insecticide-treated bait around the mounds.
    • fish, birds, and insects. As seen in the video above, floating fire ant colonies can fall prey to natural predators.
    • soap. In floating colonies, dish soap breaks the surface tension that keeps the colony afloat, and the ants drown. “Dawn is a not a registered insecticide, but it will break up the surface tension and they will sink,” says Bui, the entomologist.



The Atlantic: Yes, That’s a Huge Floating Mass of Live Fire Ants in Texas

BBC: Floating fire ants form rafts in Houston floodwaters

Nat Geo: The Architecture of Living Buildings

Nat Geo: Fire Ants, Surviving and Thriving

(extra credit!) PNAS: Fire ants self-assemble into waterproof rafts to survive floods

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