Signs
for Boxelder Bug
The clearest sign is the autumn gathering itself — large clusters of adults on the warm, sunny side of a building, looking for a way in. Source: https://extension.unh.edu/resource/boxelder-bug-fact-sheet Once inside they dot pale paint, drapes, and similar pale spots with dark waste flecks, and any bug you crush hits back with a sour smell. Source: https://extension.umn.edu/nuisance-insects/boxelder-bugs