This Invasive Ant Species Is Surging in the Southeastern U.S.

Ant trails are easy to spot and can alert you to a new infestation of ants in your home. Scout ants leave the colony to search for food, and when they find it, they lay down a pheromone trail for the other ants to follow. Soon, you can end up with a long line of ants, all following each other to a food source. However, there is an invasive species of ant that doesn’t lay scent trails, resulting in long lines of ants. The Asian needle ant is harder to detect and is expanding across the Southeastern United States. (Watch a video of Asian needle ants here.)

How Long Have Asian Needle Ants Been in North America?

The Asian needle ant (Brachyponera chinensis) is native to Japan and China. It was first discovered in the U.S. in 1932. According to the USDA, by the time experts were aware of it, the invasive ant had already made its way through at least three southeastern states. Today, the Asian needle ant has been spotted in states across the eastern U.S., from Massachusetts to Florida and as far west as Wisconsin and Indiana.

Unusual Foraging Methods of the Asian Needle Ant

One way you can identify an Asian needle ant is by its unusual foraging methods. Unlike other ant species, Asian needle ants may be found wandering around alone. These ants are little (about 0.2 inches long) and are colored dark brown to black. Their legs and the ends of their antennae are lightish orange-brown. But a better way to identify the Asian needle ants isn’t by their appearance, but by the way they walk. Unlike many other species of ants, these ants have a stealthy, low walk. Instead of lifting their legs high, Asian needle ants creep close to the ground and walk with slow and deliberate steps.

One way Asian needle ants differ from most North American ant species is how they forage for food. Most ant species send out scout ants to search for food for the colony. It’s the scout’s job to head out and search for food for the others. Once they find food, they return to the nest to alert the worker ants. To help them find their way back to the food, they leave a scent or pheromone trail behind them. Other worker ants then head out on the scent trail, find the food, and bring it back to the colony. This results in a long line of ants coming from the nest to the food, and back again.

Asian needle ants have a different and unusual method for sharing food sources with each other. Instead of creating a scent trail, a female worker ant carries a sister ant to the food source in its mandibles. When they reach the food, the ant puts the other ant down, and they both forage.

What Is the Threat to Ecosystems? How They Displace Native Ants That Help with Seed Dispersal

Asian needle ants live in forested areas, parks, residential neighborhoods, and urban areas. They don’t build ant hills but instead nest under logs or in leaf litter. You may also find them in wood piles.

According to the USDA, it has been in the past 20 years that experts have discovered the threat these invasive ants pose to native ecosystems. Asian needle ants outcompete native ants for resources, causing a reduction in native ant diversity and populations wherever Asian needle ants are found.

Most damaging is their ability to displace ant species that act as seed dispersers. Seed-dispersing ants are attracted to the seeds of certain plants and will carry the seeds far from the original plant, ensuring the diversity of the forest ecosystem. But when Asian needle ants are present, experts have found seeds from these plants are not getting dispersed at the usual rate. According to the USDA, this may have “dramatic, long-term negative effects on forest understory.”

Some People May Be Allergic to the Asian Needle Ant’s Sting

Aside from the negative environmental impact, these invasive ants have been found to cause extreme allergic reactions in some people. Asian needle ants are not aggressive towards humans. They also are not defensive towards their nests, like other ant species such as fire ants. But when an Asian needle ant is threatened, such as being caught inside a person’s clothing, shoe, or hand, it will sting.

The Asian needle ant’s sting is venomous and is said to cause intense pain. But even worse than a painful sting, some people are allergic to the venom and may experience anaphylaxis. Some of the following are common symptoms of anaphylaxis:

• Hives, itching, flushed or pale skin
• Difficulty in breathing due to swelling of the airways, tongue, and throat
• Low blood pressure (dizziness or fainting)
• Nausea, vomiting, diarrhea
• Feeling of impending doom

Experts warn anyone with known anaphylaxis reactions to other insect stings to carry an EpiPen and be cautious in areas where Asian needle ants are found.