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Ant infestation dazzles entomologists but prompts others to seek remedies

David Ziegele used chili powder around his windows because he heard it helps kill ants. It didn't work.
David Ziegele used chili powder around his windows because he heard it helps kill ants. It didn't work. (Mark Gail/the Washington Post)
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By Eric Niiler
Special to The Washington Post
Tuesday, July 20, 2010

The ants are coming. Actually they're already here, marching across kitchens, basements and bedrooms in record numbers this summer. The Washington area's wet spring and summer heat have led to a bumper crop of the tiny crawlers, looking for food wherever they can find it. And experts say they will probably be with us for the next month or two.

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"This has been a spectacular year for ants," said Mike Raupp, a professor of entomology at the University of Maryland, who has had to fend off his own ant infestation. "I've gotten more calls than any time in the past 10 years."

That will come as no surprise to David Yost of Centreville, who started seeing ants in May, including a few strays that made their way into his kitchen. So before leaving for a 12-day vacation in June, he cleaned up all the crumbs in his pantry and laid down some ant powder along the front door entryway, where an advance guard of ants had come into the townhome. When he got back from his trip, a trail of black marauders awaited him.

"The ants pushed their way through the [powder], made their way down the hall into the kitchen and into the upper shelf of the pantry, and proceeded to take over my house," Yost said. "There were thousands carrying off my cereal. That is when I got serious."

To fight back, Yost sealed every crack that he could find with silicone caulking. He has tossed out all of his cereal and keeps all of his food in the refrigerator. For the past week, he has been ant-free.

"I want to declare victory," Yost said. "But somehow I feel we may not be done with this yet."

Plenty of aphids, too

That's probably the right attitude, given that ants have been around for at least 110 million years and are native to pretty much every continent except Antarctica. There are nearly 12,000 ant species, and although they are a nuisance, they don't carry disease, they help keep away other pests and they are important scavengers, carting away dead insects and scarfing up scraps of food.

There are a few common types that area residents encounter, including carpenter ants (Camponotus pennsylvanicus), whose taste for wood can destroy porches, fences and even roofs, and the Allegheny mount builder (Formica exsectoides), which erects three-foot-high colonies and kills nearby trees with bites of formic acid.

But the main ant driving people crazy is the odorous house ant (Tapinoma sessile). These are the sugar-loving kitchen crawlers that form foraging trails in search of food. Tenacious but tiny (only a sixteenth of an inch), they build backyard colonies of about 100,000 individuals that frequently move. Squish one and you'll smell the odor of burnt coconut. They don't bite.

Raupp and other insect experts say the odorous house ant has proved so successful this year because of ideal environmental and ecological conditions. Raupp says lack of much rain lately means that the ground where ants like to build their colonies is now dry. The winter snows and spring showers, meanwhile, created a riot of plant growth this spring, and as a result, plant-sucking aphids are super-abundant, which is perfect for ants.

The odorous house ant has formed a deal of sorts with aphids. In exchange for keeping away beetles and other predators, aphids provide ants with a sweet carbohydrate secretion called honeydew. The ants like honeydew so much they often "tend" aphids, stroking them with their antennae and carrying them around.

Each odorous house ant colony sends out scouts in search of honeydew from aphids and other scale insects. It's this hunt that leads them to explore your kitchen, Raupp said.


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