lauxaniid flies are extremely common during the hotter seasons and, like a lot of other small acalyptrates, are the Platonic Ideal Fly Shape to me. this one is Sapromyza or Sapromyzosoma, and boasts one of the most recognizable looks in the family - sunny d flavored coloration with some black abdominal spots (unfortunately not visible here). it's also rubbing its hands. you can't have a fly without some hand rubbing