But now the researchers are trying a tiny phorid fly, native to a region of South America where the fire ants originated. Researchers have learned that fire ants in their home region are kept under control by as many as 23 phorid species.
The flies lay eggs on the fire ants, and the eggs hatch into maggots inside the ant and eat away at the pest's tiny brain.
The ant will get up and wander for about two weeks while the maggot feeds, said Rob Plowes, a research associate at the University of Texas at Austin.
"There is no brain left in the ant, and the ant just starts wandering aimlessly," he said.
About a month after the egg is laid, the ant's head falls off -- and a new fly emerges ready to attack another fire ant.
"They're not going to completely wipe out the fire ant, but it's a way to control their population," said Scott Ludwig, an integrated pest management specialist with Texas A&M's AgriLife Extension Service in Overton, in East Texas.
Four phorid species have been introduced in the state since 1999. They don't attack native ants or other species and have been introduced in other Gulf Coast states, Plowes told the Fort Worth Star-Telegram.
But it will take time to determine if the flies are effective in Texas, perhaps as long as a decade.
"It's not an immediate silver-bullet impact," Plowes said.