Box elder bugs are often found in clusters on the sunny side of homes. They are an overwintering pest looking for shelter inside before temperatures drop, which means they can also be seen emerging from either interior or exterior walls in the spring to get back outside. Adults are able to fly, and can come from various trees and plants, but most commonly boxelder, maple, and ash trees.
They don’t bite, spread diseases, or cause damage to homes, but they can leave a foul smell when crushed and their droppings can leave red stains.
They do not reproduce inside, and will die within a few days of being active inside if they are unable to emerge in the spring.