Box Elder Bug

They may form large aggregations while sunning themselves in areas near their host plant (e.g. on rocks, shrubs, trees, and man-made structures). This is especially a problem during the cooler months, when they sometimes invade houses and other man-made structures seeking warmth or a place to overwinter. They remain inactive inside the walls (and behind siding) while the weather is cool. When the heating systems revive them, some may falsely perceive it to be springtime and enter your home.