Boxelder bugs love to feed on various species of maple, ash, and box elder trees. They are an annoyance with their large numbers. They are found on the siding exterior and can also go inside structures to over-winter. In the fall the insects begin to congregate on walls, fences, under shrubs and prefer sunny locations. They then seek entry points to enter the structure where they settle into wall voids. They do not feed or reproduce indoors, but lay eggs only on the plants outside. Females deposit about 250 eggs per female. Simple metamorphisis from egg to adult is about 2 months. They have two generations per year. Their color is dark gray with red lines along the sides of the prothorax and along the veins of the wings.
Boxelder bugs are primarily a nuisance. They do not pose any major health threats nor do structural damage. When abundant, they can stain walls, curtains, and other surfaces with their excrement. They lay their eggs in the trees and love to soak up the sun on the siding of your house. Treating the trees is very difficult with little results. The best treatment to thin them down is to professionally treat on the siding of the structure.
Pest prevention professionals treat the exterior siding, foundation, eves and also around landscaping and shrubs where they like to congregate. An interior baseboard treatment is also recommended. Treating the surfaces where the Box Elder Bugs like to gather with a professional product can reduce the population.
The best means to prevent entrance into the home by the annoying Boxelder is exclusion. Sealing Boxelder bugs out by caulking cracks and around utility service openings, fixing broken window screens and door jams, plugging cracks in the foundation or roof as well as similar exclusion-type activities will help prevent the Boxelder from entering your home in the first place.
Once Boxelder bugs are found inside your house, the best option is to physically remove them with a vacuum or a broom and pan rather than squashing them. Though not as foul smelling as its cousin the stink bug, the Boxelder does emit an unpleasant odor when squashed. If you begin to find Boxelders in your home during fall, check around your home - especially on the south and west side because they can often be found congregating in sunny or warm areas. Use a multi-purpose shop vac to clear any outside congregations.
If possible, plan your landscape design to exclude box elder trees, ash trees and fast growing maples, since box elder bugs fed on the developing seed pods of these trees. If you prefer to plant them you should be certain of using only male varieties.