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updated: 10/18/2012 8:23 AM

Got boxelder bugs? You're not alone

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  • Boxelders seek the heat of a black letter on a metal sign in the sun in Arlington Heights.

      Boxelders seek the heat of a black letter on a metal sign in the sun in Arlington Heights.
    Bill Zars | Staff Photographer

  • A boxelder walks on the windshield inside a car in Arlington Heights.

      A boxelder walks on the windshield inside a car in Arlington Heights.
    Bill Zars | Staff Photographer


Every fall, those bugs with the distinct red markings on their wings appear as if by magic in clumps on the sides of homes, seeking the warmth of the waning season.

And this year, it is not your imagination: The number of boxelders covering windows, lurking in nooks and crannies and finding their way inside is noticeably higher.

Experts aren't really sure how much more than normal the current onslaught is, but they note it is a predictable byproduct of a hot, dry summer. Deal with it.

"It's pretty obvious when they call what they're talking about. 'These things are all over my house and the south side of my house. What do I do?'" says Brenda Dahlfors, McHenry County master gardener coordinator for the University of Illinois Extension. "This is just one of those years when they got out of control."

For the first time in years, Dahlfors added, she sprayed the south side of her house with a chemical-based product to deal with the volume of pesky bugs.

During the summer, the half-inch-long brown or black insects live on box elder trees and eat seeds. When the weather cools, they move to buildings for protection and like to bask in the sun, especially on the south- and west-facing sides.

As the temperature dips, they disappear under the siding or into cracks and crevices and find their way into wall voids. They have a knack for getting inside, and with their numbers greatly increased, the nuisance factor also goes up.

"Most people get bent out of shape with anything coming into their house they didn't put there," said Phil Nixon, an entomologist with the U of I Extension.

But as intruders go, boxelders are fairly benign.

"They don't feed on anything indoors, they don't reproduce indoors," Nixon said. "All they're looking for is a place to hang out for the winter."

Beware: They can spot curtains or wallpaper with fecal material and, if crushed, will produce a purple or red stain.

"Don't use your shoe (to squash them) on your nice white carpet," Nixon advised.

Inside, experts recommend vacuuming the critters and dumping them outside.

"If it's still warm, at least they have to find their way back to your house," Nixon said.

Caulking cracks and crevices and around window frames can also help keep them out.

"Just make sure your house is sealed up," said Kim Isaacson, Dahlfors' counterpart in Lake County. She suggested nonchemical alternatives to deal with the annoying pests, which should be gone fairly soon.

"They don't hurt people," she said.

Outside, they can simply be hosed off walls.

If more firepower is sought, Dahlfors said the U of I Extension recommends using a product containing carbaryl.

Insecticidal soap also will work, but because it has little residual control, it may have to be used every other day or possibly every day.

Repeated use of dish soap can harm or kill plants by dissolving the protective layer on the leaves or drying out the roots, Nixon cautioned.

Being coldblooded, the boxelders can't move when the thermometer dips below 50 degrees. At lower temperatures, they go dormant.

But on mild winter days, they can "wake up" and you may see them near windows seeking light and heat.

"As long as they make it into the inside of your house, they'll be there all winter," Dahlfors said.

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