Tabanus sulcifrons. I suspect this "species" may be a complex. The "early season" form has the wing membrane semi-transparent. The late season form has the wing membrane rather "milky" and contrasting and the body has a more dark reddish cast. The mesoscutum is more brownish in the early season form and more reddish in the late season form. In Maryland and Virginia, the early season form is out in July and August. The late season form is out in September and early October. The late season form has sometimes been referred to as the "carolina" form. Because the 2 forms are separated temporally, they may, in fact, be distinct species.