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Discovery News: Invasive, Fragrant Ants Crash Hawaii

11/1/2011

Odorous house ants, so-called because they smell like fresh coconut when smashed, are invading Hawaii, according to a paper in the journal Myrmecological News.

Even if you think such natural air freshener is desired, these ants are bad news for homeowners because, like most ants, the insects can be hard to evict.

Purdue University entomologist Grzegorz Buczkowski, who led the study, indicated the ants aren't going to end their Hawaii vacations anytime soon.

"Odorous house ants in Hawaii are not like they are here in natural areas where they live in small colonies," he was quoted as saying in a Purdue press release. "They are creating megacolonies like they do in urban areas. We went there to eliminate the ants, but we found it's too late to treat for them."

The ants seem to have good taste in real estate. A bunch of them are on Maui, taking up residence on the western slopes of the Haleakala volcano among some small farms, somewhat like the natural settings where the ants are found on the mainland. But despite a more natural setting in Maui, they're forming large colonies. Buczkowski said he estimated the Maui invasion is a single supercolony with more than 300 nests and multiple queens per nest covering more than 45 acres.

The potential for greater growth is even more staggering, since he found just one colony on the Purdue campus containing 5 million workers and about 25,000 queens of the tropical-smelling ants.

These insects are incredibly tough survivors. Even if you get rid of them at your house, some will invariably move next door, and then move back to your place when they feel like it.

"It's one of the worst, if not the worst, pest species in homes," Buczkowski said.

It is too soon to tell what will happen with the ants on Hawaiian islands, but the possibilities have experts concerned, given how the ant populations could impact native plant and animal species. Although the ants can spread out over a wide area, they can also establish colonies in spaces as small as a single acorn.

On the mainland, odorous house ants go dormant in winter, but with Hawaii's favorable year-round temperatures, the ants could continue to eat and expand much faster than in their native range.

It's unclear how the ants arrived on the islands, but they probably just stowed away on a ship. Buczkowski said he's still stunned they made such a long journey from their native area.

"They aren't supposed to be in Hawaii," Buczkowski said. "To go from the mainland to Hawaii, more than 2,500 miles over the sea, is amazing."


Hawaii now has several invasive and inhospitable ant species, such as Argentine and bigheaded ants, both of which are aggressive toward other types of ants.

"They didn't just invade a place that was free of ants and gain a foothold. They are in the middle of other ants and thriving," Buczkowski said. "If odorous house ants can get established there, they can get established anywhere. They could be invasive anywhere in the world."
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