Off With Their Heads

 

Fire ants at Lake Waco Wetlands decapitated by newly released flies

By Pamela Bond

Waco Tribune-Herald

June 15, 2007

Decapitated bodies lie scattered on the ground, victims of an unforeseen and lightning-fast attack that happened not in a horror film, but at the Lake Waco Wetlands.

And the victims were fire ants.

Phorid flies, which kill South American red fire ants by decapitation, were released into the wetlands Thursday by Robert Puckett, a Texas extension assistant and doctoral student at Texas A&M University.

The phorid fly is the ant’s natural predator in South America, where it is commonly called the decapitating fly, Puckett said. It kills fire ants by laying an egg in the head of the ant.

The ant’s head then falls off, killing the ant. A female fly carries 100 to 200 eggs and lays each in a different ant. These imported fire ants are not native to Texas and have disrupted the natural ecosystem, Puckett said.

Although it is unclear how they got here, the ants came to the United States in the 1930s, and now there are more of them per acre in the United States than in South America, with no natural predators here to keep the population in check.

“The whole idea is to balance things out and tip the scales back to the natural species,” Puckett said. “There are two original species of fire ants in Texas, and both were pushed out by this fire ant.”

Fire ants are also economic pests, Puckett said. Agriculturally, fire ants can cause loss of livestock and crops. In an urban setting, fire ants present problems to dwellings and electrical wires.

“One ant gets electrocuted, gives off pheromones, and other ants follow,” Puckett said. “Pretty soon, all these ants have blown a circuit. I had some blow out a circuit in my house — that’s their revenge on me.”

South American fire ants sting people, and individuals can develop allergic reactions. Young livestock, groundnesting birds (like quail) and lizards such as the Texas horned lizard also are affected by these ants.

Researchers started studying the use of phorid flies about eight years ago while looking to the ant’s natural predators to suppress populations instead of the conventional use of chemical insecticides, which can be expensive and harmful to the environment. In addition to suppressing ant populations, the flies’ presence shuts down the foraging instincts of the ants.

Field studies have had successful results, Puckett said. A pheromone given off by ants when their colony is disturbed attracts the flies. Puckett releases about 40 flies on each mound and continues to agitate the mound every 10 to 15 minutes for about 90 minutes. In the heat of summer, the ants are often slow, so Puckett uses the electrical currents of a modified cattle prod to stimulate them.

The flies Puckett uses are from a U.S. Department of Agriculture rearing facility in Gainesville, Fla. They are kept in plastic containers until Puckett is ready to gather them for a release. Because they only can develop inside the head of this specific ant, the phorid flies do not target native fire ants or other bugs. Adult flies eat nectar, but since they need so little to survive, Puckett said, they will not compete with bees.

Since the flies are small, only the size of an ant’s head at maturity, and they do not bite, Puckett said they should not be a problem for people.

“I’ve been working in Caldwell and doing this for three years, and I’ve never seen one except out in the field,” Puckett said. “They won’t be a nuisance in terms of bothering people.”

Thursday was the first phorid fly release in Waco. Puckett said he chose the wetlands because it was protected, “has a nice corridor for expansion and a high density of ant mounds.”

“I think it’s a neat deal,” said Nora Schell, program coordinator for the Lake Waco Wetlands Center. “This place is a wildlife habitat, and we’re also out here for education. If we can help, then we will. And who knows? This may be the up-and-coming suppression technique for ants.”

Puckett also chose the location because it was equidistant from release sites in College Station, Caldwell and the Dallas/Fort Worth area.

“The goal is to use select release sites that are far enough apart to let the flies do their work and spread out,” Puckett said.

The flies also have been released in Vidor, Brazoria County, Austin, Huntsville, Paris, Beeville and Livingston.

“It’s really interesting,” said John Fell, an undergraduate entomology student at Texas A&M who works with Puckett. “When we go back to determine how many flies are in the area, there’s usually 30 to 40 of them on each trap, so I’d say it’s working.”