Boxelder bugs (Boisea trivittata) are common pests that gather in large groups on trees and buildings. In the fall, they look for warm places to overwinter, often invading homes. While they do not bite or damage property, they can be a nuisance. Their excrement can stain walls and furniture, and when crushed, they release an unpleasant odor.
Boxelder bugs are easy to recognize by their black bodies and red markings. Knowing what they look like and the signs of an infestation can help you keep them out of your home.
Adult boxelder bugs are about ½ inch long. They have black bodies with bright red lines on their thorax and wings. Young boxelder bugs, called nymphs, are smaller and red with black markings. These bugs look similar to milkweed bugs, but their markings, host trees, and size help tell them apart (milkweed bugs are generally larger).
Boxelder bugs often gather in large numbers on siding, windows, and trees. In fall, they move toward homes, looking for entry points like cracks and crevices. If they get inside, they may stain fabrics and walls with their droppings. You might also notice them sunbathing on warm walls before they find a way indoors.
Boxelder bugs live on trees, feed on plant juices, and seek shelter indoors when it gets cold.
Boxelder bugs live on boxelder trees, maple trees, and ash trees. In warm months, they stay on these host trees, feeding on leaves and seeds. When the weather cools, they invade buildings, looking for a safe place to survive the winter.
Boxelder bugs eat seeds, leaves, and flowers from their host trees. They use their piercing-sucking mouthparts to drink plant juices. These insects prefer female boxelder trees because they drop more seeds.
Boxelder bugs go through three stages: egg, nymph, and adult. In spring, females lay tiny eggs on trees. In just a few days, the eggs hatch into nymphs, which grow into adults by late summer. As temperatures drop, boxelder bug adults seek shelter to overwinter.
Boxelder bugs gather in warm places like rocks, tree trunks, and buildings. They like to sunbathe and can often be found on walls, windows, and siding. If they get inside, they won’t reproduce, but they can be annoying. If disturbed, they may release a bad smell.
Boxelder bugs are not harmful to people or pets. They don’t bite, sting, or carry diseases. However, they can stain walls, furniture, and clothing with their droppings. Crushing them can also leave a bad odor. While they are mostly a nuisance pest, they can be frustrating when they gather in large groups inside a home.
The best way to stop boxelder bug infestations is to seal cracks and entry points in your home. Use caulk around windows and doors, and check for gaps in siding. If they are already inside, use a vacuum to remove them instead of crushing them. Reducing host trees (boxelder, maple, and ash) near your home can also help.
Follow these steps to keep boxelder bugs out of your home:
If boxelder bugs have taken over your home, our professional insect control experts can help. They know where to look for hiding bugs and can treat problem areas to stop the infestation.
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Learn more about other insect pests with our insect information guide.
Boxelder bugs come from areas with boxelder, maple, and ash trees. They move to warm buildings when the weather gets cold.
They are not an invasive species, but they are considered a nuisance pest because they enter homes in large numbers.
Boxelder bugs are drawn to female boxelder trees, warm buildings, and sunny walls.
Yes. Adult boxelder bugs have wings and can fly short distances.
No, boxelder bugs do not bite. But if crushed, they can stain and release an unpleasant odor.
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