Stinging Asian Needle Ants Displace Invasive Argentines in U.S.

A new invasive species is spreading across the U.S., complete with a venomous sting that causes an allergic reaction in some people. The Asian needle ant is gaining ground, and may prove to be more harmful to the environment and people than the already well-established and aggressive Argentine ant.

Argentine ants are aggressive, territorial and can create enormous "supercolonies." These consist of thousands of queens and millions of workers, and have allowed this invasive species to spread across the U.S. as it displaces native species. Until now, no other species of ant has been able to push back.

The Asian needle ant first came to the U.S. as early as the 1920s, but it's only in the past eight years that the population has exploded across the country. Eleanor Spicer-Rice, an entomologist at North Carolina State University, decided to study this population and examine what the implications would be for the rest of the U.S.

Studying different sites, Spicer-Rice found that between 2008 and 2011 Argentine ant populations dropped from a presence in 99 percent of her sites to 67 percent. At the same time the Asian needle ants expanded from nine percent to 32 percent in her study areas. Both ants only overlapped in about 15 of the sites.

Why did this happen? The Argentine ants appeared to ignore the Asian needle ants, and the new invasive species took advantage of the situation to displace the Argentine ants. Since the Asian needle ant can tolerate cooler temperatures, it had a natural advantage to overcome the other species. During winter, both ant species become dormant. Yet because of its ability to tolerate the cold, the Asian needle ant becomes active sooner and essentially gets a head start. In addition, the Asian needle ant eats other ants, so it could potentially be eating the Argentine ants.

This is bad news for the environment and people alike. Asian needle ants possess venomous stings which can cause allergic reactions in people. In addition, they drive out native species in forests that can play an important roles in seed dispersal.