Red Imported Fire Ant Nemesis Gains
Permanent Foothold in Florida By
The permanent establishment of a new species of phorid fly is
bad news for the red imported fire ant, according to
Agricultural Research Service scientists
who are working to control the aggressive ant that has spread across the
southern United States.
The establishment of the fly Pseudacteon curvatus is
significant because it is the smallest of the decapitating flies. This means it
can parasitize small worker ants--the most abundant workers in an ant colony.
Phorid fly maggots live in the head capsules of their fire ant hosts,
eventually decapitating them and pupating inside their heads. Phorid flies
attack only fire ants.
ARS scientists at the Center for Medical, Agricultural and
Veterinary Entomology in Gainesville, Fla., recently reported that they
collected P. curvatus flies from a research site southwest of
Gainesville, one year after the flies were initially released. This confirms
the first overwinter survival and permanent establishment of P. curvatus
on red imported fire ants in the United States.
Sanford D. Porter, acting research leader of the ARS
Imported Fire Ant and Household
Insects Research Unit in Gainesville, and Juan Briano, director of the ARS
South American Biological Control
Laboratory in Argentina, originally collected P. curvatus in
Argentina in October 2001. The flies were released at the Gainesville site in
March 2003 and have been found in increasing numbers ever since.
According to Porter, another biotype of P. curvatus was
previously established on hybrid fire ants, but it did not prefer red fire
ants. The more recent establishment came from a biotype that prefers the much
more abundant red imported fire ants.
There are about 20 species of phorid flies in South America that
specifically attack fire ants. P. curvatus and P. tricuspis are
the only ones known to be established here.
P. curvatus is one more natural enemy of fire ants that
scientists can add to their arsenal of biological control agents. Fire ant
populations are much greater in the United States than they are in South
America, where natural enemies appear to keep them from being the dominant
ARS is the U.S. Department of
Agriculture's chief scientific research agency.