Asian Needle Ants Displacing Other Aggressive Invaders

Feb. 11, 2013 — Researchers from North Carolina State University have found that one of the most aggressive invasive ant species in the United States -- the Argentine ant -- appears to have met its match in the Asian needle ant. Specifically, the researchers have found that the Asian needle ant is successfully displacing Argentine ants in an urban environment, indicating that the Asian needle ant -- with its venomous sting -- may be the next invasive species to see a population boom.

Asian needle ant stinging a termite.

 (Credit: Benoit Guenard)

In the world of invasive species, the Argentine ant (Linepithema humile) is a success story. Its aggressive, territorial behavior and ability to create huge "supercolonies" -- consisting of thousands of queens and millions of workers -- have enabled the Argentine ant to spread across the United States, displacing native species and changing ecosystems to suit its needs. No other ant species had been seen successfully pushing back -- until now.

In 2008, while watching a supercolony of Argentine ants in an urban environment, former NC State Ph.D. student Dr. Eleanor Spicer Rice noticed that Asian needle ants (Pachycondyla chinensis) were living and working in the area. This was surprising because Argentine ants normally do not tolerate any other ant species in their territory, so Spicer Rice decided to investigate further.

Read on:  http://www.sciencedaily.com/releases/2013/02/130211102304.htm

Invasive Ant Dying Out

One of the world's worst invasive species, the Argentine ant, is mysteriously disappearing from New Zealand.

The Argentine ant poses a huge risk to horticulture and is a threat to native species.

They attack birds, have been known to eat lizards in New Zealand and the World Conservation Union classed them as one of the world's 100 worst invasive species.

The small, brown insects were first found in New Zealand in 1990 and have spread throughout the North Island, usually attracted to warm climates like Northland and Hawke's Bay. Their colonies reach as far south as Christchurch.

But, the population has just started dying off, though the reason for their deaths is unclear, Victoria University associate professor Phil Lester said.

Lester and masters student Meghan Cooling concluded the species naturally collapses after about 10 to 20 years.

The pair assessed about 150 sites throughout the country that have been populated by the ants.

The colonies disappeared from at least 40 per cent of the sites and populations had significantly shrunk at the other sites, Lester said.

They discovered some dead ants, but believed the others had decomposed or been eaten.

"At some sites they've disappeared all together and other native ants have reinvaded these areas," Lester said.

It was unclear why the invasive ant was disappearing, but Lester suspected it was due to a virus of some sort.

"Because they're collapsing on their own the country could save millions," he said.

When the species was first discovered in New Zealand the Government estimated the ants would cost about $68 million a year in pest control, Lester said.

They have destroyed farms overseas and killed off other species, but they haven't been so disastrous in New Zealand.

But they could potentially threaten the viticulture and horticultural industries if populations got out of hand.

If they were to reach Department of Conservation protected islands the results could be disastrous.

The ants are about 2-3 millimetres long and produce multiple queens and can form huge super-colonies that extend for thousands of kilometres, according to the Biosecurity New Zealand website.

They can bite and cause a reaction in some people.


http://www.stuff.co.nz/environment/6069396/Invasive-ant-dying-out