Bald-faced hornets construct large, enclosed, football-shaped nests out of a papery grey material, typically suspended from tree branches, shrubs, or the eaves of buildings. Colonies can grow to several hundred workers by late summer and are known for defending the nest aggressively, often stinging repeatedly when threatened.
Because a disturbed nest can trigger a coordinated attack from many workers at once, and stings can cause serious allergic reactions in sensitive individuals, nest removal is a task for trained pest control technicians using appropriate protective gear rather than a homeowner.