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Six-legged invaders poised to take over Georgia
The man showing James Morgan around the vacant assisted-living duplex pointed at the baseboards: “This is what we’re dealing with.”
In the empty room, the problem was obvious. Piles of dust covered the white baseboards like dark snow, collecting in drifts against the wall and spilling out four and five inches onto the floor. It was the same in the living room and the bathroom—mounds of black dust against tan laminate tile. But when Morgan leaned down for a closer look, he realized it wasn’t dust; it was death. The carcasses of thousands of reddish-brown ants, no more than an eighth of an inch long, heaped against the base of the wall. In Morgan’s sixteen years as an extension agent, he had never seen anything approaching the number of ants indicated by the mass of corpses on the floor.
Morgan stepped out into a mid-August morning in Albany, Georgia, and walked around the foundation of the duplex, looking for a point of entry. He surveyed the ground for ant trails, snapping reference photos with his iPhone. The humidity from the grass, damp from the prior night’s rain, was enough to fog the lens. Soon Morgan determined that the mystery ants were getting in through the back door. Now he needed to find the source.
Morgan passed a stack of brush and a woodpile, both covered with ants, and entered a shed on the edge of a wooded area, about 150 feet from the duplex. The shed was filled with old refrigerators, stoves, rusty pieces of tin, and forgotten lumber. Morgan pulled out some of the metal and wood and quickly jumped back as thousands of the insects swarmed out.
Outside the shed, Morgan again looked for a trail. Most Southerners are familiar with Argentine ants, which travel in tight lines, following a path of pheromones from one place to the other. But these ants staggered about randomly, moving in crazy, drunken zigzags across the grass.
Until Morgan knew exactly what he was dealing with, he couldn’t do anything to get the ants under control. So he scooped up a vial of the dead insects and sent the tiny corpses, along with the reference photos, to the University of Georgia’s Griffin Experimental Station. And he waited.
Two days later, the mailer containing Morgan’s vial of dead ants joined the stacks of insect samples on the desk of Daniel Suiter, a professor of entomology in the University of Georgia’s Department of Entomology. Morgan’s package was a priority. For years, Suiter had been watching a swarming ant species called “tawny crazy ants”—named for their reddish-brown color and erratic foraging patterns—spread across the Gulf Coast. These ants formed colonies estimated to contain between 15 and 20 billion ants per acre—so large and dense that their clusters can short out electrical boxes. Suiter knew it was only a matter of time before the tawnys hit Georgia.
But even using a high-powered microscope, Suiter could not be certain that Morgan’s ants were the same as the Gulf Coast invaders. Identification this specific, down to the species, requires a lifetime of training because the differences between the 12,761 classified ant species are, well, tiny, in both size and magnitude. So Suiter, a generalist, packed the ants back into their vial and mailed them to the Mississippi Entomological Museum at Mississippi State University. There, taxonomist Joe MacGown noted that Morgan’s ants were wingless and hairy—their thick, barbed hairs growing in pairs were characteristic of the genus Nylandaria, and the smaller, finer hairs on the middle of the body cut the field to only two exotic species. The tawny, orangish-red coloration helped him narrow the species to fulva—Nylandaria fulva, an invasive ant from South America. MacGown also read Morgan’s description of the ants’ behavior. The massive colony size coupled with the ants’ rapid and fitful movement indicated that these ants were indeed tawnys.
So how did an ant get to Georgia from South America?
Scientists believe that the tawny crazy ant quickly became a dominant part of local wildlife in South America, especially in Colombia, where it spread disastrously, causing damage to the area’s ecology and agriculture. The United States has a huge appetite for South American coffee, bananas, sugarcane, and building materials, and a tiny ant could easily stow away on a massive U.S.-bound freighter without being detected.
The first significant populations of tawnys are believed to have landed in the U.S. around 1990. Hundreds promptly took over the second floor of a Miami hospital. They were soon spotted on the University of Miami campus “foraging on sidewalks and running up and down tree trunks,” according to a paper published in Transactions of the American Entomological Society in 2000. From there, the ants spread into the Everglades National Park, Jacksonville, Fort Lauderdale, Sarasota, and up and down the Florida coast. In 2002 they were discovered in an industrial complex about fourteen miles outside of Houston. The discovery was made by a pest-control professional named Tom Rasberry, and in the region, the insects took Rasberry’s name. By 2013 the Rasberry crazy ants could be found in twenty-four Texas counties.
These ants spread with the ebb and flow of human traffic. Because they nest in existing structures, piles of debris, and potted plants instead of outdoor hills and tunnels, people unwittingly pack them up with the moving van. In fact, according to entomologists at the Louisiana State University Agricultural Center, human traffic is probably how the tawnys ended up in Mississippi. Then Louisiana.
By the end of 2010, Georgia and Alabama were the only two Gulf Coast–area states unoccupied. Of course, by the time Morgan showed up at the nursing home in Albany, that had changed.
Tawny crazy ants have no natural predators in North America. Fortunately for Atlanta and most of North Georgia, our winters are probably too cold for this tropical ant. But in cities like Albany, the farthest north that tawnys have been sighted in such great numbers, there’s nothing in nature to hold them in check. Their multi-queened colonies enable them to reproduce rapidly, spreading over the landscape and crowding out native ants and other insects from food resources. Scientists now believe crazy ants use venom to kill fire ants, a South American species that invaded the South in the 1930s.
Because tawny crazy ants do not build their own nests but rather exploit preexisting cavities and debris-filled areas, undisturbed spaces are a haven, vulnerable only to insecticides—most of which have little effect on the tiny interlopers. Standard professional pesticides will keep the ants at bay for a month or two at most, but they don’t kill the colony. According to Rasberry, exterminators in Texas had to apply for a special exemption from the EPA to use fipronil, because at the time it was the only insecticide that could stop the tawnys. (It’s still the most effective.)
As with most insects, cleaning up trash and loose debris is the first line of defense against the tawnys. So Morgan asked the owners of the nursing home to pick up the brush piles and to look into removing the stack of wood behind the duplex. He also suggested filling the cracks in the concrete foundations and installing door sweeps to make sure the ants stayed out of living areas.
Unfortunately, cleaning up isn’t enough. To keep these ants under control, it’s not just the yard that must be treated, but the surrounding area as well. Without chemicals, that would mean clear-cutting the forest. Instead, the nursing-home owners sprayed insecticides around the foundations, moved the woodpile, and crossed their fingers. “It’s been over a month,” Morgan says. “They haven’t asked me to come back.”
This article originally appeared in our April 2014 issue.