Crazy Ants vs. Fire Ants

Crazy ants secrete formic acid and smear it on their bodies to neutralize fire-ant venom.

In our 2014 magazine, we reported that South American crazy ants are damaging homes and electric equipment as they overrun parts of the southeastern U.S., and they’re also displacing another invader: red fire ants. Since then, UT Austin scientists have figured out how crazy ants clobber fire ants with IronMan-like defenses that protect them against the main tool in a fire ant’s arsenal. 

Crazy ants and red imported fire ants both come from Argentina and Brazil, where their ranges have overlapped for a long time.

Fire ants dominate most ant species by dabbing them with a powerful venom that anyone who has been stung by a fire ant has felt. In a feat of evolutionary one-upmanship, crazy ants secrete formic acid and smear it on their bodies in a way that neutralizes fire-ant venom. This chemical counter-weapon may act as armor. It makes crazy ants nearly invincible in skirmishes with fire ants over food and nesting sites.

Crazy ants and red imported fire ants both come from Argentina and Brazil, where their ranges have overlapped for a long time. There, it’s like an insect version of “Rock, Paper, Scissors”: fire ants dominate most other ant species including species that dominate crazy ants, but crazy ants beat fire ants. Here, though, the detoxifying abilities of the crazy ant and the absence of the other species put fire ants at a disadvantage.

“As this plays out, unless something new and different happens, crazy ants are going to displace fire ants from much of the Gulf Coast region of the southeastern U.S. and become the new ecologically dominant invasive ant species,” says Ed LeBrun, a research associate with the Texas Invasive Species Research Program at the Brackenridge Field Laboratory. 

See our video of crazy ants detoxifying fire ants and read more about the study.