An aggressive species of ant may be losing ground in North America to a more aggressive -- and potentially dangerous -- species, according to a new study.
Argentine ants long ago established dominance in many parts of the continent, thanks to their ability to form "super colonies" consisting of thousands of ants. But the species seems to have met its match in the Asian needle ant, which was observed stealing turf from the Argentine ant over four years in a North Carolina office park.
"I was helping someone out with a project observing Argentine ants in 2008 when I noticed Asian ants hanging around in the area," said Eleanor Spicer Rice, senior science editor at Verdant Word, who was a doctoral student at North Carolina State University. The presence of any other ant around the territorial Argentine species was unusual, so Dr. Spicer Rice decided to study both species.
In 2008, Argentine ants populated 99 percent of sites in the office park, while Asian ants were present in only 9 percent. By 2011, Argentine ants were found in just 67 percent of the sites, while the Asian ants had spread to 32 percent. The two species shared 15 sites. The paper was published in PLoS One.
The danger for humans is that the Asian ants have venomous stings that can cause weeks of burning and itching. Victims who are allergic to the sting can suffer more severe reactions. Argentine ants are known for crowding out other small species of plants and lizards, but do not pose a direct threat to humans.
The researchers think that the Asian ants have an advantage over the Argentines because they are active in cool weather, when the Argentine ant rests. Asian ants are thought to have come to North America in the 1930s and have since spread to Alabama, New York, Oregon and Virginia, among other states.
Correction: February 26, 2013, Tuesday
This article has been revised to reflect the following correction: An earlier version of this article misstated where Eleanor Spicer Rice works as a senior science editor. It is Verdant Word, not Verdant World.
This article originally appeared in The New York Times.