This is a mating pair of Tiger Bee Flies. This native fly is found throughout the state and late July into early August is the peak of adult activity. They don't bother people and use carpenter bee larvae as food for their young. If your yard or street hasn't had a noticeable uptick in carpenter bee activity this year or last, perhaps some dead trees in nearby woods provided more habitat for carpenter bee nesting to increase the population (and that of this nest parasite as well).

Miri