USDA Fights Invasive Fire Ants With Flies

Maryann Mott
for National Geographic News
December 21, 2005

Not all good things come in small packages.

The red imported fire ant—a mere quarter of an inch (less than a centimeter) in size—is a 6-billion-dollar-a-year problem in the United States.

The reddish-brown venomous insects short-circuit appliances, damage traffic lights, sting people, and threaten endangered bird and reptile species.

To get the burgeoning ant population under control, entomologists at the U.S. Department of Agriculture's (USDA) Imported Fire Ant and Household Insects Research Unit in Gainesville, Florida, are using a tiny winged warrior: the phorid fly.

The flies swoop down on ants, depositing an egg underneath their skin. Within days fly maggots are born and release an enzyme that decapitates their ant host. The fly then completes its development using the ant's head as a safe hideaway.

When the ants see the adult flies, they run and hide, freeze, or twist upside down to avoid getting stung, says Sanford Porter, an entomologist at the USDA's research unit in Gainesville.

Formidable Foe

Red imported fire ants (Solenopsis invicta) were accidentally carried over on ships from South America in the early 1900s. The invaders now infest 320 million acres (129.5 million hectares) in 14 states, including Texas, California, New Mexico, and Puerto Rico.

Fire ants are a formidable foe because of their high reproductive rate. A single-queen colony can have 250,000 workers. In some states there are up to 10 colonies per acre, each producing 5,000 offspring annually.

Robert Vander Meer works with Porter at the USDA's insect unit in Gainsville.

In Florida, he said, the most common reason air conditioners break down is because fire ants short-circuit the electrical components. They also gnaw on wires for sprinkler systems and traffic lights.

Scientists are not sure why the ants are drawn to electrical systems, but the strange attraction wreaks havoc and is considered a major economic impact of the insects' spread.

Continued on Next Page >>


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