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Invasion of the ants

South Carolina may be next in line for a new species of invasive insects

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In 2005, one Florida researcher discovered a shocking infestation when he went to his parents' winter home in Palm Beach Gardens to prepare for their arrival. Stepping through the home, he turned on the bathtub faucet and witnessed thousands of ants pouring out from the pipes. This would not be an isolated incident with this new species.

The tawny crazy ant, known formally as the Nylanderia fulva, is a relatively new transplant to the United States. By most accounts, this invasive species native to South America was first recorded in Texas in 2002, but soon spread throughout counties in the Southeast. In the U.S. Virgin Islands, they've been known to swarm houses, covering the walls of homes inside and out. Residents reportedly swept up dustpans full of dead ants every day. Feeding on smaller insects and vertebrates and honeydew secreted by aphids, these ants have become a serious pest in Colombia, causing chickens to die of asphyxia and even attacking cattle. And as they spread northward from their native home, it appears South Carolina is their next stop.

When worlds collide

"The first time I saw them, we got some reports and identified them from male specimens. I had heard about them, but I was a little skeptical, so an extension agent and myself went to visit a site and thought, 'Well, I hope we can really find them,'" says Joe A. MacGown, scientific illustrator and curatorial assistant at the Mississippi Entomological Museum. "We're driving down this little gravelly road, and I'm looking out the window of the car in the passenger seat. Looking at the road, it seemed to be vibrating. It was just ants walking."

Known for their rapid, erratic movements, the tawny crazy ant was first noted in Mississippi by MacGown and his fellow researchers in fall 2009. Visiting an infested site in Hancock County at the southernmost part of the state, MacGown found a thriving colony of crazy ants. They had damaged electrical boxes and filled the walls of a nearby camper, causing a metal wall to bulge outward. Tawny crazy ants are known to be especially attracted to electrical equipment, chewing through wires and causing devices to short circuit. Even after multiple applications of pesticides, the homeowners had barely made a dent in the invading population.

Joe A. MacGown - PROVIDED
  • Provided
  • Joe A. MacGown

"At this one building I saw, I filled up a trash bag with dead ants in about 30 seconds, a complete trash bag just from a pile of ants that was up against the building," says MacGown. "So they're easy to kill individually, but there's so many that it's a matter of how much pesticide can I spray legally and safely."

According to MacGown, the ideal method of combating tawny crazy ants is to identify a new population while it's still young and wipe them out right away — something that he acknowledges is easier said than done. Currently in South Carolina, a team of researchers at Clemson are readying to launch an effort to survey areas along the state's southern coast to see if the ants have arrived and document their habits — their end goal being early control of the species before they number in the hundreds of millions. Just last week, Tim Davis, a researcher at the University of Georgia's Chatham County extension office, told Georgia Public Broadcasting that tawny crazy ants are believed to have arrived in the state through the port in Savannah and are expected to spread as has been witnessed in other states.

"Maybe there's only a queen or two that starts a little colony and, of course, no one's going to notice that right away. Conditions have to be suitable for that queen to actually start a colony and lay those eggs and have workers. Then it may take a few years before anybody even notices they're in the area," says MacGown. "They may start out really small and go unnoticed, but they do seem to build populations very rapidly. Once there is a large population, people notice those right away because they're huge. They're mind-bogglingly huge. You're talking about areas where you just walk anywhere and your feet are covered in ants."

But don't think of the tawny crazy ants as an entire blanket of insects sweeping across the border. MacGown says in Mississippi and other areas, they're heavily populated in certain small pockets, but they don't extend across the entire coastline of Mississippi. No one is walking down the beach getting attacked by ants. The main concern to humans is that by reshaping our environment to suit our own needs, we've created an environment fit for an invasion.

"When we take natural settings and make it to where it's usable for us, it's not really greatly usable for most native species. It's limited to what species can live in a lawn versus a natural prairie or a woodland," says MacGown. "So you can have pockets of natural habitat within an urban or suburban yard, around trees, or on the edge of something, but generally not many native species really do well at living in those conditions. It kind of leaves a void for species to come in that are more general with their habitat preference like the tawny crazy ant and others."

Human introduction

To understand how new species are introduced to areas they would have otherwise never known, look no further than humans. Whether through commerce, travel, or simply our own silly desires to reshape our environment, the spread of foreign animals is usually the fault of man.

A prime example of this involves a drug manufacturer by the name of Eugene Schieffelin, who in 1890 released a flock of 60 European starlings he had shipped from overseas. His goal was simple, if also very foolish: He wanted to introduce every bird mentioned in the works of William Shakespeare to America. While his initial attempts failed, Schieffelin's dream of starlings in the United States eventually came to fruition — and with them disease and major damage to crops.

The introduction of the tawny crazy ant, as with many other invasive species, can also be blamed on humans. With the spread of global commerce, we find our ports flush with fresh shipments from all over the world, but often humans end up unloading more than we bargained for, especially when it comes to insects.

"They have to get here first. That's the trick. And we do that. People move things. Almost every one of these things has come in with commerce," says Brian Scholtens, a biology professor at the College of Charleston specializing in entomology and plant-insect interactions. "We have an entire federal agency, APHIS (Animal and Plant Health Inspection Service), that regulates or tries to regulate the import of organisms that we don't want. Charleston has an APHIS office, and they regularly inspect cargo shipments that come in. If they find things that shouldn't be there, they'll require the fumigation of the ship, but there's no way they can inspect every container that comes in. It's just impossible."

According to Scholtens, there's no great estimate of how many insect species there really are in South Carolina, and when it comes to invasive species, we often miss particular groups until they become well established. In the case of the red fire ant, a well-known non-native species that showed up in South Carolina in the 1960s and spread through the state, the arrival of the tawny crazy ant could spell trouble. Both species prefer open fields and lawns, but in a ground battle between them, crazy ants have the advantage. Most people are familiar with the sting of a red fire ant, but crazy ants have the rare ability to resist such an attack. By producing formic acid and rubbing it on their bodies, crazy ants are able to neutralize the venom from fire ant stings. "So in a war between the two, as it were, tawny crazy ants have a new weapon. They have a great defense," says Scholtens. "And so they can then overwhelm the fire ants because the fire ants' main weapon doesn't work any more. And so that's how they can actually displace this ant that nobody else can deal with."

For humans, this may sound like a win-win situation. Tawny crazy ants, which don't sting, replace fire ants. But there are pluses and minuses to any new invasion.

"Some people would say, 'Oh yeah, let it come in and displace all those fire ants and get rid of them so that we don't have to worry about the stings.' But here's the deal: The tawny crazy ant is also incredibly good at nesting just about anywhere including in structures," says Scholtens. "Even though they don't destroy homes, they'll nest all over the place and they like things like electrical boxes. They chew through electrical wires and they short electrical wires and it ends up causing lots of problems. Ecologically, one of the big minuses is that it is so effective in displacing species, just taking up space, that it will likely displace even more species than the fire ant did when it showed up."

the tawny crazy ant may be small, but it's mighty - JOE MACGOWN
  • Joe MacGown
  • the tawny crazy ant may be small, but it's mighty

Now, you may be thinking, "This is why we have pesticides," but the solution isn't that simple. As homeowners have learned in other parts of the world, spraying for these pests is usually only a temporary solution, especially when they find a million more crazy ants waiting in the wings. Also, while pesticides are a great way to manage some insect populations, they also effectively create an entirely new generation of bugs resistant to that specific poison. Much like how viruses become resistant to new vaccines, insects with a natural resistance to pesticides go on to foster a fresh crop of offspring with the same characteristics.

"That's what the pesticide companies depend on. Patents only last so long," says Scholtens. "Where would a pesticide company be if nothing ever became resistant and the same pesticide could be used for years and years and years?"

A new world

When considering native and non-native species, how far back should we look? By this point, most people living in the Southeast are accustomed to fire ants, but they can still be considered an invasive insect. According to Scholtens, there is a great deal of argument over what is native to North America and what isn't. No real records of what existed in the United States were kept until long after the Europeans arrived. He points out that the Native Americans knew what was here and what was brought over from the Old World, but no one really asked them. And as different populations have invaded foreign nations and products manufactured overseas are brought to our shores, new species have come along with them.

A face that only a queen ant would love - JOE MACGOWN
  • Joe MacGown
  • A face that only a queen ant would love

"Charleston is, of course, especially positioned because we're a major port. We have thousands of containers coming in every month. All of those are potentially invasive species paths," says Scholtens. "It just happens because we move things all over the world. It's because we import Toyotas and because we import citrus fruit and because we import bananas and because we send stuff over to other countries. Europe has a bunch of introductions from North America. Asia has a bunch of introductions from North America. We're doing the same thing to them that they're doing to us. And it's just one of those things that we have to live with because of our commerce."

Now, with global trade in addition to a changing climate, we're faced with an ever-shifting environment. Temperatures in some areas will rise. Certain cities will dry out. Some will become washed over by a rising tide. And the insects that thrive in those environments will have a new territory in which to expand. While researchers can't really predict what species will become established in a certain area, they can determine which environments are suitable for hosting invasive species. And a lot of this is based on climate. Tawny crazy ants aren't going to cause a problem in the northern states or Canada. It's too cold there. But by comparing the climate of South Carolina and other areas where invasive species thrive, we can better understand what to expect.

"We've had at least a couple of species that have expanded significantly into the state and we see some things showing up as Southern migrants a lot more often than they used to," says Scholtens. "We're already seeing the movement happening."

So what options does that leave us? We face a changing environment and the possibility of new challenges in all shapes and sizes. As humans have spread across the globe, bringing trade, disease, and a host of new species to foreign shores, we've been left with few other options but to adapt or perish. Now, with a new challenge possibly on the horizon, it's time to change again — whether it be combating rising sea levels, understanding global warming, or simply keeping ants out of our circuit boxes.

"For them, it's like a little cavity in nature and it's perfect. Only when there's electrical equipment in there, it tends to short things out and that's when it becomes a problem for us," says Scholtens. "So what we're going to have to do in many of these cases is learn how to modify our equipment to make it inhospitable for these ants because, honestly, we're not getting rid of them. They're here and so we have to learn to adapt just like they've adapted. That's what it comes down to and that's what humans have done throughout history."

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