When flooded, fire ant colonies form living rafts that can float for weeks — hydrophobic, with the queen safe at the center.
JournalPNAS — Mlot et al. (2011)2011Share →
Red Imported Fire Ant
Solenopsis invicta
Builds living rafts during floods. Floats for weeks. Costs the US $6 billion a year.
Curated and rated by Sheriff Six-Legs and The Wild Pest field team · Six Legs Score™ (90/100, Apex Outlaw tier) · Published Apr 25, 2026 · Updated Apr 28, 2026 · Released CC BY 4.0
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When floods hit the southern US, fire ants do something extraordinary: they grip each other and form a LIVING RAFT that can float for weeks, with the queen and brood at the center. The raft is hydrophobic — water can't penetrate. The species is one of the most invasive on Earth and causes $6 billion in annual US damage.
Size
Workers 2-6 mm; queens 8 mm
Lifespan
Workers 60-180 days; queens 2-7 years
Range
Native South America; invasive in southern US, Australia, China, Caribbean
Diet
Omnivorous — insects, plants, nectar, oil, sweets, dead vertebrates
Found in
Disturbed open ground: fields, lawns, roadsides, electrical equipment
Field guide
Solenopsis invicta is native to South America but has become one of the most damaging invasive species in the world. Introduced to the southern US around 1933 (likely Mobile, Alabama) via cargo shipping, the species now blankets the southeastern US, has invaded Australia, China, the Philippines, and parts of the Caribbean. Annual US damage exceeds $6 billion in agricultural losses, livestock injuries, and electrical equipment damage (fire ants nest in transformers and HVAC systems). The species is famous for an extraordinary survival strategy: when flooding hits a colony, the workers link together using mandibles and tarsal claws to form a living raft that floats indefinitely. The raft is genuinely hydrophobic — air pockets between the bodies repel water. The queen and brood ride safely on top. A 2011 study by the Georgia Tech Hu lab demonstrated that fire-ant rafts behave as both elastic solids (when small forces are applied) and viscous fluids (under sustained stress) — the same dual behavior of self-healing materials being researched for engineering applications.
5 wild facts on file
Fire ants cause over $6 billion in annual damage to the US economy — agricultural, electrical, and medical costs combined.
AgencyUSDA APHISShare →
Fire ants nest in electrical transformers and HVAC equipment, causing widespread short-circuits and equipment failures.
AgencyUSDA APHISShare →
Fire ant rafts behave as both solid and liquid simultaneously — Georgia Tech researchers study them as a model for self-healing materials.
JournalMlot et al. (2011). PNAS2011Share →
Fire ant stings cause distinctive pustules and intense burning — the venom is unique in being almost entirely alkaloid (solenopsin), not protein.
JournalToxicon journalShare →
Cultural file
Fire ants are the subject of perhaps the most intensive ant-eradication program in human history — the USDA Imported Fire Ant Quarantine has spent decades attempting to slow their northern spread. The species is the basis of US Department of Defense studies in swarm robotics, where the raft-formation behavior models how autonomous drones might self-organize during emergencies.
Sources
JournalMlot et al. (2011). PNAS2011AgencyUSDA APHIS — Fire Ants
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