Benoit Guenard / North Carolina State University
An Asian needle ant stings a termite in this photo from North Carolina State University. The invasive species are displacing invasive Argentine ants.
A stinging ant from Asia is spreading with a vengeance across the United States and may prove more devastating to people and the environment than the well-established aggressive Argentine ant currently is, according to new research.
"While Argentine ants cause a lot of damage, Asian needle ants are a really big health threat to humans," Eleanor Spicer-Rice, an entomologist at North Carolina State University, told NBC News.
The invaders from Asia pack a venomous sting that can cause an allergic reaction in some people. Spicer-Rice said the sting produces small welts that get surrounded by a rash. It itches and hurts when scratched.
"It is one of those aggravating bites," she said.
In North Carolina, people routinely go to the hospital with severe allergic reactions "because they are reaching into a woodpile and getting stung by Asian needle ants and they don’t know what it is and what is happening to them. They don’t realize the Asian needle ants are here," Spicer-Rice noted.
Spread of the needle
Historic records indicate the ants were in the U.S. as early as the 1920s, but for reasons that are not yet clear, their population has exploded in the past 8 years and they are spreading across the country, Spicer-Rice said.
She first took note of the Asian needle ants in 2008 while studying a supercolony of Argentine ants in Raleigh. This was unusual. Argentine ants are typically aggressive to other ant species and push them out of their territory. She started to investigate.
Between 2008 and 2011, she found that Argentine ant populations dropped from a presence in 99 percent of the sites within her study area to 67 percent, while the Asian needle ants expanded from 9 percent to 32 percent. Both ants overlap in about 15 of the sites.
Why? It appears that the Asian needle ants are able to tolerate cooler temperatures better than the Argentine ants, Spicer-Rice and colleagues report in a paper published online Feb. 8 in the journal PLoS One.
All ants essentially hibernate when wintertime hits, but the Asian needle ants "wake up before other ant species wake up," Spicer-Rice explained.
This head start allows them to build nests, find sources of food, and start reproducing before the other ants get going. This displaces Argentine ants in urban environments as well as native ants in forested areas.
Ant eats ant?
Other behavioral traits may also play to the Asian needle ant’s advantage. For example, the Asian needle ants eat other ants.
"While the Argentine ants aren’t bothering the Asian needle ants for one reason or another, the Asian needle ants may be eating the Argentine ants," said Spicer-Rice, who is preparing a paper on the behavior of the ants for publication.
For now, she said people need to learn what Asian needle ants are and that they may be in their yards. Her research shows that toxic baits are effective at killing the Asian needle ants. If widely used, it could slow their spread.
And spreading the ants are. Spicer-Rice works on a citizen-science project called School of Ants where people send in ants collected in their backyards to North Carolina State University for identification. Today, "Asian needle ants are the most common ants found," she said. "Five years ago, nobody even knew what an Asian needle ant was."
John Roach is a contributing writer for NBC News. To learn more about him, check out his website.