You have boxelder bugs in your house. During the fall, boxelder bugs seek protected spots to spend the winter. They may hibernate under tree bark, rocks, debris, and the crevices and cracks around the siding and foundation of your house. They often crawl under the siding or shingles to hibernate in wall voids, attics, or other unheated areas in your house.

As long as the boxelder bugs stay cold, they remain inactive. However, warm days during late winter or early spring causes them to wake up out of their hibernation. As they try to get outside, they may inadvertently move into the home's interior where they become trapped. They die within several days. Despite circumstantial evidence, they do not lay eggs or reproduce inside buildings. The boxelder bugs that you are seeing now entered your home last fall.

Fortunately, these insects are harmless. They do not infest food, clothing, or cause structural damage. Boxelder bugs can excrete a red liquid that sometimes stains furniture and drapes. You may also find them around your houseplants but any feeding damage should be minimal. (They prefer to feed on the seeds of boxelder trees).

When boxelder bugs are in attics, wall voids, or other hidden areas, there is no practical way to eliminate them. Once boxelder bugs are inside your house, the best way to control them is by vacuuming or sweeping them. You can kill large numbers of boxelder bugs by spraying them with an insecticide (e.g., pyrethrins or tetramethrin). However, insecticides will not prevent boxelder bugs that are still in wall voids or other crevices from invading your house.

During the early spring, you may also find large numbers of boxelder bugs clustered on the outside of your home. They have just came out of their hibernating spots as they prepare to fly away to feed. These bugs will not attempt to enter your home. Killing them in spring will not decrease the population of boxelder bugs next fall.

The best way to control boxelder bugs is exclude them from entering your home through physical or insecticidal means in the fall. Caulk cracks and crevices. Put screens on all roof vents and crawl spaces. You can also spray the outside of your house with a residual insecticide. For more information, refer to the fact sheet, Boxelder Bugs.