Phorid flies are tiny flies that lay their eggs in the bodies of fire ant workers. Larvae hatch from the eggs and eventually move into the ants' heads, where they eat the tissue inside the head. When the larvae transform to adult flies (pupation), the ants' heads fall off, hence the popular name, "decapitating" flies. Phorid flies are a natural enemy of fire ants in their native habitat of South America and help keep their populations low. Phorids don't kill more than 2-3% of fire ants in a colony, but they make fire ants less competitive, by changing fire ant behavior. Phorid flies will not eliminate fire ants, but they are an additional source of control that cannot be found in many areas. They also cause stress to the fire ant colony, which may leave fire ants more susceptible to pesticides, other natural enemies or disease, or environmental factors. Several phorid fly species have been released in most of the Southern states in the past few years and more are in the pipeline; phorids are not commercially available. It is still too early to tell whether phorids will affect fire ant populations in important ways in the fire ant-infested areas of the U.S. See also FAQ #827: "Are there any biological controls out for imported fire ants? I heard about a fly that is supposed to kill fire ants. What's the story on that?"

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