Fire Ants Falling to Acid-Covered Crazy Ants

Residents of the United States’ Gulf Coast are getting used to the sting of tawny crazy ants and starting to forget about the fire ants that dominated the region since the 1930s. These invasive tawny crazy ants, which have been rapidly displacing colonies of fire ants in many southern U.S. states, employ a unique chemical defense that allows them to best fire ants in battle, according to a new study. Edward LeBrun and colleagues observed that crazy ants cover themselves with abdominal gland secretions that effectively detoxify their wounds after they’ve been stung by fire ants. Upon being stung, crazy ants stand on their hind and middle legs, curl their modified abdomens underneath their bodies and begin grooming themselves with secreted formic acid, according to the researchers.

This detoxification behavior allowed 98 percent of tawny crazy ants stung by fire ants to survive, compared to 48 percent without the detoxification behavior, they say. And because the native ranges of both invasive ant species overlap in northern Argentina, Paraguay and southern Brazil, LeBrun and his colleagues suggest that the crazy ant’s potent defense system evolved there, under fierce competition for resources with fire ants and native South American species. The researchers’ findings also highlight the importance of understanding invasive species’ behavior in their native ecosystems in order to improve eradication efforts abroad.