Lighter overall than the similar F. tricosa. Touching the distal edge of the reniform spot is a small brown or gray area with 3 or 4 regularly-spaced sharp points like the top of a picket fence (that same area in F. tricosa is black, smaller, and with an irregular outline). See comparison images
of both species.
central portion of North America, north to QC, ON, SK (absent from MB and both Canadian coasts)
adults fly from July to September
pinned adult image
and other info (Moths of North Dakota)