Parasitic Ants May Debilitate Fire Ants

Agricultural Research Service scientists have confirmed that a parasitic ant that helps control fire ants in Argentina could help curb the spread of fire ants in the southern United States.

The destructive red fire ant, Solenopsis invicta, now infests more than 300 million acres in 12 states throughout the South and Puerto Rico. It is thought to have arrived in the soil of potted plants or in the water ballast tanks of ships from South America in the 1920s. It has since become well established, threatening a variety of wildlife, damaging electrical systems and causing a nuisance to people.

Researchers at ARS’ South American Biological Control Laboratory in Buenos Aires, Argentina, report that the parasitic ant Solenopsis daguerrei habitually lives in the nests of fire ants. Like one queen usurping another in a palace coup, the parasitic queen--or sometimes virgin females--attach themselves to the S. invicta queen and divert resources from her. This parasitic behavior is so well disguised that the fire ant workers care for the imposter queen and her brood as if they were their own. Eventually, the fire ant queen becomes unable to produce eggs, and the colony dies.

This suggests that S. daguerrei might be an effective form of biological control for fire ants in the United States. But first, researchers must complete field host-range studies under way in Argentina to confirm its host-specificity. If it is found to exclusively parasitize fire ant species, this will affirm its viability as a possible biological control for red fire ants.

So far, researchers sampled a total of 4,316 mostly fire ant colonies in Argentina. S. daguerrei was found to exclusively inhabit 161 of the fire ant colonies. This preliminary data confirms that S. daguerrei does appear to be host-specific to the fire ant genus Solenopsis. ARS researchers in Gainesville, Fla., are currently studying the parasitic ant under quarantine safeguards.

ARS is the U.S. Department of Agriculture’s chief scientific research agency.

Scientific contact: Juan Briano, ARS South American Biological Control Laboratory, Buenos Aires, Argentina, phone 54-11-4662-0999, fax ext. 104, jabriano@mail.retina.ar.