There are many different types of mydas fly, and it took me some time as well. When I narrowed it down I asked an entomologist friend from UT and he confirmed it was a Mydas fly. They actually kill and eat many of the pests you don't want; The adults are predatory, feeding on caterpillars, other flies, bees and true bugs and even the occasional wasp. They also feed on nectar which many flies do. Larvae live in rotting wood and probably feed on beetle larvae. Flies do not sting, but they will probably bite if mishandled.
Andy