Horse flies are attracted to a variety of smells and visual cues, such as the smell of animals, particularly horses. They are also drawn to sweat and other human secretions; movement like running or waving arms; shiny surfaces that reflect light; dark colors, especially blue; heat sources like sunlight or body warmth; and moisture. Horse flies have an advanced vision system which they use to identify their hosts. Additionally, they use UV wavelengths for navigation purposes since some host species have UV-reflective patches on their bodies. It is important to note that horse flies are very difficult pests to control because many repellents do not work effectively against them. The best way to prevent horse fly infestations is through physical exclusion by covering windows with screens and keeping doors closed when possible.