[header] How to get rid of boxelder bugs outside [title] Use a perimeter treatment. [step] A perimeter treatment is formulated for use around the exterior of the house and other structures. Spray one of these insecticides around all possible openings, including the entire perimeter of the home, attic vents, basement windows, cellars, windows, doors, siding, garden sheds, and garages. 
[substeps] While this will not destroy all the boxelder bugs living in your yard, it will prevent them from getting inside. The bugs that pass over the insecticide barrier will also die, thereby reducing the population in your yard.