The wings are held partially open at rest, forming a V-shape. These are cylindrical in cross-section, and taper from the rear to the head. Horn fly adults typically occur on cattle, but may infest horses and game elk. Adults spend most of their life on their hosts, congregating on the back and shoulders of the animal, or on the underside during hot days to escape the heat. Unlike stable flies, horn flies rarely bite people.
Horn flies are pests only in pasture or rangeland systems.
Adults become active early in the spring and spend most of their lives on the backs of cattle. Both sexes feed on cattle blood by piercing the skin with the proboscis. The blood meal is required for egg production. Females lay 8 - 13 eggs per day on average. The maximum lifespan of a female is 21 days, so a single female could potentially lay 100-200 eggs throughout her life.