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Public Radio's Environmental News Magazine (follow us on Google News)

Fire Ants

Air Date: Week of

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Across the southeastern U.S., red imported fire ants make a nuisance of themselves by biting anything that gets in their way and wreaking havoc on the native ant populations. Host Steve Curwood talks with research entomologist Sanford Porter about one promising technique for controlling the fire ants: killer flies.


CURWOOD: It's Living on Earth, I'm Steve Curwood. Red fire ants have made the southeastern United States a dangerous place to walk barefoot since the 1940s. These aggressive, pesky ants will bite anything that stands still long enough, including people, livestock, crops, or even outdoor air conditioners. In an attempt to stop the spread of these ants, scientists are looking to the ants' old nemeses from their native continent. I'm joined now by Sanford Porter, a research entomologist with the United States Department of Agriculture.

CURWOOD: For our listeners who don't live in the southeast, how big of a problem are these little guys? I mean, I take it they aren't just your sort of typical show up at a picnic uninvited type of ants, huh?

PORTER: Well, the problem is that they're absolutely everywhere. If you walk around in your back yard with your bare feet it's easy to get stung. So, for the average person it's an aggravation. But for little kids, for example, it's a fairly serious problem. A little two-year-old will climb onto a fire ant mound and the fire ants just swarm up by the hundreds and thousands and the poor little kid can get bitten hundreds of times before he can get off.

CURWOOD: What's it like to get stung by the ants? I mean, I live in New Hampshire. I've been bitten by the ants that are in an anthill here. It's no fun.

PORTER: It's about like a mosquito bite or a pinprick. They hurt for about a minute or two, and then about 24 hours later they form a little sterile pustule that looks like a pimple. And the problem is not one bite, but it's easy to get stung by the fire ants dozens or even hundreds of times.

CURWOOD: Now, why are these fire ants so pesky? Is this how they hunt? I mean, they go out and they eat huge creatures?

PORTER: Absolutely. They are premiere mass recruiting social insects, and that's how they do it. They find some food, they go back to their nest-mates, and they say "There's lots of food over here." And pretty soon you have hundreds and thousands of ants out there trying to carry the food back.

CURWOOD: These fire ants have no natural enemies here, but in their native South America there are things that keep these ants in check. And I understand that you've got a laboratory there, in Gainesville, Florida, that has enlisted a certain fly in the fight against fire ants. How exactly do they wage this battle?

PORTER: Well, the flies are something that we're very excited about. The flies are little, itty bitty flies, about the size of a head of a fire ant. And there is a reason for that, and what the flies do is come in, hover a couple of millimeters above the ants, and as soon as they get in just the right position they inject an egg into the ant. And the egg hatches in a couple of days, moves into the ant's head, where the little maggot swims around for a few weeks. And when it gets mature, then it will release an enzyme that causes the fire ant's head to fall off.

CURWOOD: Oh, my.

PORTER: And when the head falls off, then the little fly maggot eats everything in the fire ant's head and pupates like a butterfly. So, it's using a fire ant head like a cocoon. A few weeks later, the adult fly pops out and starts looking for more ants.

CURWOOD: What kind of defenses do these fire ants have against this decapitating fly?

PORTER: Well, the fire ants will first run and hide as quick as they can, if they can. If they can't hide fast enough, then they'll freeze. And they'll, of course, stop foraging while the flies are attacking.

CURWOOD: So, let me see if I've got this right. Fire ants are out having a good time. And it's like one of the gang looks up and sees a cop car, like these flies, and everybody scatters, huh?

PORTER: (Laughs) Oh, exactly. Exactly. There's some kind of an air raid alarm that the ants put out that says we're under an air raid, everybody scatter.

CURWOOD: These flies actually don't kill that many of these fire ants.

PORTER: Right. They probably only kill a few percent of the colony. But the biggest impact is on the ability of the ants to collect food. So while the ants are hiding from the flies, that means that our native ants can be out there eating the food that the fire ants would have normally eaten. And then when that happens, the native ants can compete with fire ants at other times, as well. Basically, what we're trying to do is shift the ecological balance in favor of our native ants.

CURWOOD: There is the obvious concern that if you bring in a non-native species to fight these fire ants, which are already a non-native species, you could have more problems down the road.

PORTER: Yes, and that's something that we are always very concerned about. So we looked at how the flies affected other kinds of ants and what kinds of things they were attracted to. They're not attracted to people, they're not attracted to animals, they're not attracted to plants or our food or our refuse or carrion. They don't vector diseases. The flies are extremely specific. They're like little guided missiles, that when they run out of fire ants to eat they basically just die.

CURWOOD: Now, when do you think you're going to be able to release some of these red fire ant avengers on a larger scale?

PORTER: Well, we've already begun that here in Gainesville. About three years ago, we began the releases. We were thrilled to find them out a few hundred yards and that they survived the winter. And then the second year, we found them out three or four miles. And then, we went out just last November and we found them out another eight to sixteen miles. So they are now occupying almost 1,000 square miles around Gainesville, Florida.

CURWOOD: And what's happened to the fire ant population around Gainesville, Florida?

PORTER: Ah, excellent question. That is something that we're just beginning to look at. Last spring, we set out a bunch of test sites just outside the wavefront of the advancing flies, and this fall, they've moved into the test sites and it will probably be a couple of years before we can assess the impacts.

CURWOOD: Sanford Porter is a research entomologist with the United States Department of Agriculture in Gainesville, Florida. Thank you, sir.

PORTER: You're welcome, Steve.

(Music up and under: "Them!" THE UNINVITED, VOLUME 3)



Fire Ant Problem animation
Behavioral and Community Interaction of Phorid Flies and Fire Ants">


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