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Ant Rafting

Short answer: Red imported fire ants (Solenopsis invicta) come from the flood-prone wetlands of Brazil. When water rises, a colony can link itself into a floating raft that carries workers, brood and the queen.

In a 2011 PNAS study, Mlot, Tovey and Hu of Georgia Tech filmed raft-building and measured how it works. Ants grip each other jaw-to-leg and leg-to-leg. A single ant's cuticle is only mildly water-repellent, but linking together boosts the colony's water repellency, much like weaving a waterproof fabric. Air trapped around and between the ants cut the raft's average density by about 75%, to about 0.2 g/mL. That trapped air also lets the ants on the bottom breathe, so they rarely drown. About half the ants form the bottom layer. Ants on top walk to the edge and get trapped there by their neighbors, which is how the raft grows. The paper describes rafts floating for days, and Hu's group told reporters they can last up to about three weeks, though most begin to fall apart after a week. Ants also build bridges, ladders and chains in the same way.

VideoWrite-up3 sources
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What should you know about Ant Rafting?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. Trapped air cuts a fire-ant raft's average density by about 75%.

    DD-662-F01 · Write-up · Exhibit C (Air does the floating)

  2. Fire ants grip each other jaw-to-leg and leg-to-leg to form rafts.

    DD-662-F02 · Write-up · Exhibit B (How they link)

Video transcript: Ant Rafting: A Colony That Floats

DID YOU KNOW? When floods threaten their colonies, fire ants perform one of nature's most remarkable survival feats. They build living bridges and rafts out of their own bodies! By linking their legs and jaws together, thousands of ants form a buoyant, interlocking structure that can float for weeks on water. The ants on the bottom grip tightly while trapping air pockets between them, creating a waterproof layer that keeps the colony afloat. Others move freely across the surface to stabilize or repair the raft as it drifts. NOW YOU KNOW!

Burned-in captions, read frame by frame (see transcript.md) · 25.7s Reel ·

Video coming soonAnt Rafting · Instagram Reel
Ant Rafting: A Colony That Floats Instagram Reel · · 25.7s

The write-up

A colony that floats. Fire ants link legs and jaws into waterproof rafts.

  1. Exhibit A

    Built for floods

    Fire ants (Solenopsis invicta) come from flood-prone Brazilian wetlands and raft whole colonies, including the queen and brood.

  2. Exhibit B

    How they link

    Ants grip each other jaw-to-leg and leg-to-leg, weaving a sheet that's far more water-repellent than any single ant.

  3. Exhibit C

    Air does the floating

    Trapped air cut a raft's average density by about 75%, and it lets the bottom ants breathe underwater.

  4. Exhibit D

    How it grows

    Ants on top walk to the edge and get pinned there by their neighbors, which adds to the raft.

  5. Exhibit E

    How long

    The study describes rafts floating for days. Researchers say up to about three weeks, though most start breaking up after a week.

Questions people ask about Ant Rafting

Which ant was studied building rafts?

The red imported fire ant, Solenopsis invicta.

Source: Write-up · Exhibit A (Built for floods) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; Science News: Teamwork keeps fire ants high and dry

Where are fire ants originally from?

Flood-prone wetlands of Brazil.

Source: Write-up · Exhibit A (Built for floods) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; Science News: Teamwork keeps fire ants high and dry

About how much does trapped air cut a raft's density?

About 75%, to roughly 0.2 g/mL.

Source: Write-up · Exhibit C (Air does the floating) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS

How do the ants link together?

Mandibles and tarsi.

Source: Write-up · Exhibit B (How they link) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; National Geographic Education (2017): Floating fire ants mess with Texas

How long did the 2011 study say rafts float?

For days. Other accounts say up to about three weeks.

Source: Write-up · Exhibit E (How long) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; National Geographic Education (2017): Floating fire ants mess with Texas

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. Which ant was studied building rafts?

    1. Solenopsis invicta
    2. Atta cephalotes
    3. Formica rufa
    4. Camponotus pennsylvanicus
    Show the answer

    Answer: A. Solenopsis invicta The red imported fire ant, Solenopsis invicta. Source: Write-up · Exhibit A (Built for floods) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; Science News: Teamwork keeps fire ants high and dry

  2. Where are fire ants originally from?

    1. Brazil
    2. Texas
    3. Australia
    4. China
    Show the answer

    Answer: A. Brazil Flood-prone wetlands of Brazil. Source: Write-up · Exhibit A (Built for floods) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; Science News: Teamwork keeps fire ants high and dry

  3. About how much does trapped air cut a raft's density?

    1. About 75%
    2. About 5%
    3. About 25%
    4. 100%
    Show the answer

    Answer: A. About 75% About 75%, to roughly 0.2 g/mL. Source: Write-up · Exhibit C (Air does the floating) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS

  4. How do the ants link together?

    1. Jaw-to-leg and leg-to-leg
    2. With silk threads
    3. With glue from their abdomens
    4. They don't touch
    Show the answer

    Answer: A. Jaw-to-leg and leg-to-leg Mandibles and tarsi. Source: Write-up · Exhibit B (How they link) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; National Geographic Education (2017): Floating fire ants mess with Texas

  5. How long did the 2011 study say rafts float?

    1. For days
    2. For minutes
    3. For years
    4. Only seconds
    Show the answer

    Answer: A. For days For days. Other accounts say up to about three weeks. Source: Write-up · Exhibit E (How long) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; National Geographic Education (2017): Floating fire ants mess with Texas

Cite this case file

Easterling, Marcus. "Ant Rafting." The Detail Department (DetailEnjoyer), case file DD-662, last updated Oct 16, 2025. https://detailenjoyer.com/case/ant-rafting/

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