I’m pretty sure this is a sculptured resin bee (Megachile sculpturalis), a fairly common, solitary bee in the Megachilidae family (the leafcutter, mason, and resin bees, and allies). We see them on a variety of flowers in our yard. This one is on the Verbena bonariensis (tall verbena or Brazilian vervain) and that seems to be a favorite for these bees. Like most bees, they are not at all agresive and much more likely to fly away from you than bother you in any way. I think they’re quite pretty, with their furry thorax and sculptured abdomen.