They swarm to the sunny sides of homes during the Fall looking for a place to spend the winter and often show up all winter inside homes on warm winter days.
Adult boxelder bugs are about ½” long, black with orange or red markings. Immature insects are bright red and sometimes are found clustered on shrubbery or tree trunks.Boxelder bugs primarily feed on the seeds of box elder trees but will also eat on maple and ash seeds. When the summers are long and hot the numbers of these insects seem to skyrocket and they can severely stain siding, walls, and windows with their excrements.
Prevention
Cutting down trees in your yard will rarely help the problem significantly as these insects can fly long distances to reach wintering sites. Sealing cracks and crevices in your home with caulk or other sealants may help but it is very difficult to seal every crack and these insects are expert at finding entry points.
There are many pesticides registered for use against these insects but treating a home can be very difficult without proper equipment. Timing is also critical since most homeowner products have a fairly short effectiveness. Most homeowners contact a professional pest management company to discuss the problem and take advantage of their expertise to save time and money