FORT WORTH - Researchers in Texas are trying an unusual approach to combat fire ants - deploying parasitic flies that turn the pesky and economically costly insects into zombies whose heads fall off.

The biting, territorial fire ants cost the Texas economy about $1 billion annually by damaging electrical equipment, according to a Texas A&M study. They can also threaten young calves.

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.

"There is no brain left in the ant, and the ant just starts wandering aimlessly," said Rob Plowes, a research associate at the University of Texas at Austin.

Soon, the ant's head falls off - and a new fly emerges ready to attack another fire ant.

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 a decade. "It's not an immediate silver-bullet impact," Plowes said.

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