Another moth that for a while I thought might be Xestia or Feltia. It is similar to Eueretagrotis perattentus but differs by the +/- rectangular black mark near the edge of the lower quarter of the forewing and broad costa with no marks for at least two-thirds of its length (there are usually some small black marks in Eueretagrotis perattentus).
The sigmoid dart is a moth of the family Noctuidae. It is found in eastern North America species. In southern Canada it is found from Ontario to central Saskatchewan, and in the United States from Maine to Minnesota, south to western Maryland, Ohio, and western Kentucky. It has recently been recorded from North Carolina and Tennessee.
The wingspan is about 40 mm. Adults are on wing from June to July.