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- Natural enemies of the fire ant are being imported from
South America to combat the invasive pests in the United States, report
scientists focused on eradicating the critters. Fire ants reside on more
than 300 million acres across 12 states and Puerto Rico.
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- "We believe imported fire ants have flourished in
the United States because they have no natural enemies here. We're trying
to change that by working with state cooperators to introduce natural enemies,"
said David Williams, a scientist with the U.S. Department of Agriculture
Agricultural Research Service.
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- It is thought that fire ants came into the United States
in the 1930s as castaways aboard ships from South America. The pests are
known for their aggressive behavior, nasty stings and huge mounds. Their
prolific breeding has allowed them to displace many native ants.
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- The ants attack anything that disturbs their colonies,
making them a threat to small children who have slow reaction to the ants'
sting. The ants can also cause potholes by undermining roads and can destroy
electrical contacts.
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- Researchers, who have had no luck eradicating the pests,
have turned to the ants' natural enemies from South America as a means
to control them. These include a disease-causing microorganism and a decapitating
fly.
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- These tiny flies lay eggs in fire ants that cause the
ants' head to fall off.
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- The microorganism, Thelohania solenopsae, infects ant
colonies and causes disease. The worker ants probably transfer the pathogen
to the queen through food exchange. The disease reduces her weight, she
lays fewer eggs and the colonies get smaller, said Williams.
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- The microorganism does not harm plants or native ant
species. After several years of testing, it has only been found in red
and black imported fire ants.
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- "Since our first release in 1998 in Florida, Thelonia
has spread to more than 75 percent of the colonies we're monitoring,"
said Williams. "But it will take longer to see a major impact."
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- The other notable enemy is a fly, Pseudacteon tricuspus
which pierces an ant's outer cuticle and deposits an egg underneath. The
egg quickly hatches into a fly maggot that moves into the ant's head. When
the maggot is mature, it releases an enzyme that causes the ant's head
to fall off.
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- "One female phorid fly usually contains a hundred
or more torpedo-shaped eggs, so she can make multiple attacks," said
Sanford Porter, an entomologist at the Agricultural Research Service.
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