Fortunately, the season for deer flies is rather short, usually four to five weeks in June or July, and three to four weeks in August for horse flies. If the problem lasts six to eight weeks, there may be several species present or that species lasts longer than most. Humans are better able to protect themselves than wild or domestic animals by swatting flies away and by using repellents. The greatest deer and horse fly activity occurs on warm, sunny days when there is little or no wind. A slight drop in temperature or a sudden breeze reduces biting attacks.
Deer flies seem to be attracted to moving objects and dark shapes.
Some reported good results of these odorless, non-chemical, adhesive patches. The patches are three inches wide by six inches long, and are worn on the back of a cap to trap and hold biting deer flies. Patches worked best when moving. W. Ten Mile Road, Leroy, Michigan 49655. Shipping is free and within 24 hours.