Aggiornamento 15/05/2007

Animals out of their native habitat can greatly damage the local ecosystem. Most of the time, introduced species are heavily limited by adverse conditions to which they are unable to adapt. Sometimes, however, in the absence of predators and parasites, an invasive species can colonize the new land and cause extensive damage.
One of the most dangerous pests in the world today are "fire ants," Solenopsis invicta, commonly known as the red imported fire ant (RIFA). They have been accidentally introduced into the United States from their native range in South America via Brazilian cargo in Alabama, in the 1930s. Now they are common in all of the Southern U.S and they are spreading north, with the help of global warming.

Fire ants nest in the soil, often near moist areas, and like warm weather. They are common everywhere in their range, from city gardens to open woodlands. The colony produces a mound about 20-40 cm high, housing millions of ants in a large underground complex, that usually host more than one queen. The workers are very small, 2 to 6 mm and reddish-brown in colour. These insects feed mostly on young plants, seeds, and sometimes small insects. Fire ants, being extremely aggressive, often attack small animals and can kill them with venom, sincronizing their attack with pheromones. They bite the skin to get a grip and then sting (from the abdomen) all at the same time, injecting a toxic alkaloid (piperidine). For humans this is a painful sting, and multiple stings can be deadly to sensitive individuals. Children, pets and cattle can be seriously harmed by fire ants and several casualties are reported in the last years. In Texas, for example, fire ants cause extensive damage for more than 300 million USD each year. In the whole US the sum reach the incredible amount of 2 billion USD.
Fire Ants are are being fought in the southern United States since the 1950s with fire and poison. Now venomous bait, species-specific treatment by modern pest control companies (like Pest Shield Pest Control in San Antonio, Texas), and biological control are the main weapons against the invasive insect. Phorid flies have been imported as an attempt to control fire ants by natural means. The genus Pseudacteon, an ant-decapitating fly, is a parasite of the ant in South America. They lay eggs in the head of the ant; their larvae eat the contents of the host's head and emerge several days later. The phorid flies have been widely introduced throughout the U. S. Southeast, with a project managed by Texas Cooperative Extension of the Texas A&M University. Not all introductions have been successful, but these flies have been established in some sites in every Southeastern state. Local actions involving people are carried on constantly, like Doc. Molly E. Keck Community Wide Fire Ant Management Program in Texas, teaching local people how to fight ants on their own property. By now, despite all the experimented techniques, they can be controlled but not eradicated.
The ants are not just a nuisance for humans. They contribute to extinction of local species, disturbing bird nesting on the ground, reptiles, amphibians and many insects, extensively damaging the ecosystem. Many recreational (outdoor activities, park use, children playing) and economical (cattle, tourism) activities have been greatly affected by the presence of fire ants. Since 2001, this species has been spread to eastern Australia, the Philippines, Taiwan, and China. There are fears of a possible appearance of the fire ants species in Southern Europe too.

On invading species see:
the swamp invader, the story of Louisiana crayfish 
an overview of invasive species in Europe, especially Italy  

Many thanks to the family Evans, Brent, Carolyn, Laurel and Jonah, Robert and Kim Abernethy, Molly E. Keck, Dominique Alongi and all the staff of Pest Shield Pest Control - www.pestshieldpestcontrol.com