Fire ants may have first entered the United States during the 1930s aboard ships coming from South America. Over the years their populations have exploded, in many cases displacing native ants. The fire ants attack anything that disturbs their colonies, making them dangerous to small children. They also cause damage to electrical contacts, cause potholes in roads, and damage agricultural fields.

"We believe imported fire ants have flourished in the Unites States because they have no natural enemies here," says David Williams of the U.S. Department of Agriculture. Researchers have identified two of the ants' natural predators and enemies from South America as a means to controlling the population. These natural enemies—a disease-causing microorganism and a decapitating fly—are being imported to help reduce the number of fire ants.

Read these general articles:

• U.S. imports fire ant enemies
• U.S. South fights fire ants with pathogen

Learn about the Problem

One of the classic cases of an imported species—also called a nonindigenous or exotic species—without a natural predator is the case of rabbits in Australia. Read a history of the problem and Louis Pasteur's attempt to solve it in Pasteur in Australia. The following activities help you examine the problem: Biology Explorer: S and J Curves—Compare the growth curves of rabbits in America and in Australia to understand what happens to a population without a natural enemy. Biology Explorer: Introducing a Virus—See how a virus might be used to create a "natural enemy" for the rabbits. Biology Explorer: Effect of Food Supply—See how the food supply might be used to control the run-away rabbit population.

Think about the Problem

• Are all nonindigenous species invasive of their new ecosystems? Support your answer with examples.
• What are some of the possible negative side-effects of introducing a natural enemy to control a nonindigenous species?

For the Teacher: Extending the Problem

• Texas Imported Fire Ant Research and Management Plan: This entire site is dedicated to the problem of the fire ants in the southern United States. It provides additional information about the ants and gives information to residents for dealing with them.
  
  
• Control of the Rabbit in Australia: This site gives information about the history, economic and environmental impact, biological control, and cultural perceptions of rabbits in Australia.
  
  
• National Biological Information Infrastructure: This site has a whole section dedicated to Invasive Species, including the fire ant. The site provides extensive information and visuals, and links to various databases.
  
  
• USGS Nonindigenous Aquatic Species: This site tracks newly identified nonindigenous aquatic species within the United States. It provides scientific reports, data sets, and general information.