Fire ant

Imported red fire ants (Solenopsis invicta) are a South American species. "Imported" refers to the fact that they were accidentally introduced into the United States in the 1930s, having hitched a ride on a ship to Mobile, Alabama. They are more aggressive than most native species of ants and their sting is quite painful. A person typically encounters them by accidentally stepping into one of their mounds, which causes the ants to swarm up the person's legs, attacking en masse.

Fire ants are efficient competitors to other ants, and have been successful at enlarging their range in the U.S., gradually spreading north and west despite intense efforts to stop them. Today they are found in most of the southern states, including Texas. It is not uncommon for several fire ant mounds to appear suddenly in a suburban yard or a farmer's field, seemingly overnight.

(At least one community uses the presence of fire ants as a publicity opportunity: Marshall, Texas, hosts an annual fire ant festival.)

Fire ants are still on the move, too, often traveling from one area to another in turf, root balls of nursery plants, and other agricultural products. They are a pest not only because of the physical pain they can inflict, but also because their mound-building acitivity can damage plant roots and lead to loss of crops. Although their stings are rarely life-threatening to humans and other large animals, they can kill smaller animals such as birds.

At present fire ants in the US can be controlled but not eradicated. A number of products are available which can be used on a mound-by-mound basis to destroy the ants' colonies when they appear. With all such efforts, it is important to reach and kill the queen (or queens), which may be as deep as six feet underground; otherwise she may simply move a short distance away and quickly establish a new colony.

Some exciting work is being done in the area of biological controls. One promising avenue involves introducing, into infested areas, a species of phorid fly found in the ants' native habitat that parasitizes the ants. A fascinating description of the parasitization mechanism may be found at this external site: http://www.inetport.com/~texasbot/fireants.htm. Large-scale use of such controls is for the future, though, and it remains to be seen how successful it will be.

An outbreak of the ants in Queensland, Australia, occurred in 2001. It is believed the ants were present in shipping containers. Only after sustained government inaction became a major public issue did substantial control measures begin to be put into place. A five year AU$145m eradication programme has begun involving the employment of 500 controllers and the baiting of 100,000 homes. The first of 12 chemical treatment rounds in the Brisbane area was 80 per cent successful according to Queensland Primary Industries Minister Henry Palaszczuk.

Official Queensland site: " class="external">http://www.dpi.qld.gov.au/fireants/

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