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The world's smallest known flies, phorid flies, are five times smaller than fruit flies. This tiny fly species (genus Pseudacteon) features prominently in fire ant control programs in the southeastern United States. The end result of a phorid fly attack is decapitation of the fire ant. No other species of ant is bothered by the Pseudacteon fly.
The female phorid fly is equipped with a needlelike egg-laying tube. She attacks a fire ant and deposits her eggs inside the ant's body. When the eggs hatch, the larvae eat their way into the brain. They consume the entire brain contents as they grow. About one month after being laid, they release an enzyme, causing the host ant's head to fall off. The mature flies emerge, ready to mate.
Biological Control Potential
The Pseudacteon fly is native to Argentina, the same South American region that fire ants originated from. Researchers began to see the possibility of using the species-particular parasite as a biological control agent against fire ants in the late 1990s. They began importing phorid flies for research, mass reproduction and release.
Fire ants are an accidentally imported invasive species. Black fire ants arrived in Mobile, Alabama, in 1918; red fire ants arrived in the southeastern United States in the 1930s. They create a serious health hazard for humans, animals and plants. Hundreds of ants will attack when their nests are disturbed, stinging repeatedly. Severe medical reactions are common. Fire ants displace native ant species and now cover most or all of Alabama, Florida, Georgia, South Carolina, Tennessee, Mississippi, Arkansas, Texas and Oklahoma. There is hope that introducing the phorid fly to these regions will have a beneficial impact in the fight against fire ants.
Pseudacteon Field Studies
Much has been learned about the Pseudacteon fly through field studies conducted by the University of Texas. They've learned that the tiny fly attacks while fire ants are foraging, reducing the amount of food taken back to the colony. Released flies reproduce rapidly and can spread as far as 30 miles per year. There is still much to be learned about life cycle, laboratory breeding, interaction of species and how the 23 species that attack fire ants differ.