CORVALLIS, Ore. — As cooler weather arrives, insects and spiders begin searching for warm, protected places to spend the winter — and homes often provide the perfect refuge.
"Just like us, they’re coming inside to get warm. They’re not feeding on homes or humans. Most are minding their own business. They aren’t aggressive toward people, not even the spiders.”
“Just like us, they’re coming inside to get warm,” said Brooke Edmunds, horticulturist with the Oregon State University Extension Service. “They’re not feeding on homes or humans. Most are minding their own business. They aren’t aggressive toward people, not even the spiders.”
Boxelder bugs can gather by the thousands on the south- and west-facing walls of houses and outbuildings, while spiders roaming in search of mates may alarm homeowners. Of the 700 to 800 species of spiders in Oregon, only the black widow poses a serious risk to people. Black widows are more common in Southern Oregon and east of the Cascades than in the Willamette Valley, according to Gail Langellotto, OSU professor of horticulture.
Research shows that hobo spiders are not venomous, though bites may cause mild irritation. The brown recluse, a venomous species often feared, does not live in Oregon.
Other insects frequently spotted indoors include:
- Brown marmorated stink bugs, shield-shaped pests that feed on crops and ornamentals.
- Mediterranean seed bugs, tan insects with black triangular and diamond-shaped markings, which feed on grass and weed seeds.
- Springtails, tiny soil dwellers that jump several inches using a tail-like mechanism. They thrive in damp environments and may appear in sinks, drains, basements and crawl spaces but soon die without moisture.
Prevention tips
To help keep pests outside, Edmunds recommends sealing cracks and gaps around doors and windows, repairing screens and removing debris or leaf litter near foundations. If insects do enter, vacuum them up and dispose of the bag or contents in a bucket of soapy water.
“Insects get through spaces so small you don’t even think about them,” Edmunds said. “You want to keep as many out as possible and then vacuum up the rest.”
There’s no need to vacuum spiders, which are beneficial in gardens and can be gently moved back outdoors.
Insecticide sprays are generally not recommended. They are often no more effective than vacuuming, and repeated applications may be needed. At best, pesticides provide only temporary relief. For serious infestations, pyrethroid treatments around building foundations may be used, but applications should be made by a licensed professional.
Previously titled Insects and spiders out to find shelter for winter
