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| A dive-bombing phorid fly (center) takes aim to lay an egg behind a fire ant’s head. When the egg hatches, the larva will crawl into the ant’s head, which will fall off and become food for the larva. |
Until the decapitating flies showed up, Buck Aultman had no way
to rid his 20-acre pasture of its pox of fire ant mounds. “You
can’t afford to spread fire ant bait out here,” he said.
But Aultman’s pasture is now home to a swarm of fierce little
flies that may be better than a pesticide. The Tift County
farmer
is taking part in a research study involving the first Georgia
release of phorid flies.
About the size of gnats, phorid flies are Brazilian parasitic
flies. They feed on fire ants in their reproductive cycle, said
Sanford Porter, an entomologist with the U.S. Department of
Agriculture’s Agricultural Research Service in Gainesville,
Fla.
The flies have been successfully introduced in Florida and pose
no threat to people or anything else in the environment. “The
only things they’re attracted to are fire ants,” Porter said.
“For that matter, they’re attracted only to imported fire
ants.”
Off With Their Heads!
Each female phorid fly carries about 200 eggs, Porter said. In
the blink of an eye, she lays an egg right behind the head of a
fire ant, releasing a deadly enzyme in the process.
In about two weeks, the egg hatches, and the small larva crawls
into the head of the fire ant, which falls off — really. The
larva then feeds, grows, pupates and emerges as an adult from
the
cleaned-out shell of the fire ant’s head. And the deadly cycle
starts again.
The 7,000 flies released near Tifton could spread as far as five
miles within the next year, said Wayne Gardener, an entomologist
with the University of Georgia College of Agricultural and
Environmental Sciences.
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| After eating the contents of the fire ant’s head, a new adult phorid fly emerges to continue a cycle that makes fire ants scurry and humans smile. |
A Boundless Buffet
For phorid flies, Georgia is a boundless buffet of fire ants.
Since arriving in the United States from Brazil in the 1930s,
fire ants have had no diseases or insects to hamper them. So
far,
their spread has been limited only by cold weather.
But scientists hope phorid flies can change that.
“Phorid flies won’t kill out fire ant colonies,” said Beverly
Sparks, an UGA Extension Service entomologist. “They will
parasitize the ants and reduce the numbers within a colony.”
Sparks said the tiny dive bombers harass fire ants endlessly,
too, trying to inject their egg time bombs into them. “The
result
is that the ants spend a lot more time in a defensive posture
and
less time foraging,” she said. “The colony is thus weakened and
hopefully less competitive with native ant species.”
A Slow Process
Scientists don’t know how well the flies will survive and how
effectively they’ll reduce fire ant numbers. They’ll closely
watch the fire ant mounds near the release site. “This is an
expensive research project,” Sparks said. “Releases of these
flies cost us nearly three dollars per fly.”
Since phorid flies spread only a few miles a year, their spread
will require a long time unless more funds can be provided to
support further releases. “We’d probably have to get local
governments involved in the process,” Gardner said. “Maybe even
the state government.”
That would be fine with Aultman. “Anything to control fire
ants,” he said. “I’m all for it.”
