Mexican mint marigold is a hit, but what IS this thing?

Earlier this year I planted Mexican mint marigold, which can be grown here in Texas as a replacement for tarragon. It actually does taste fairly close to tarragon, though whenever I plant something experimental there is always a part of me that is absolutely sure that the plant is mislabeled and what I'm growing is actually poisonous, hallucinogenic or something else undesirable. That's the problem with growing your own food, at least for someone who reads too much Dean Koontz and Stephen King.

My MMM is now blooming, so I went out to take some pictures of it's purtiness. It was in full sun at the time and the nectar was obviously flowing, because it was a nectar-feeding-species bonanza. A blooming Golden Corral for insects. There were bees, bee-like things and butterflies, all swarming around. The nectar must have been good stuff because they were willing to let me take pictures. It was Friday afternoon. Maybe they were having happy hour.

Bees

Metallic green bee?

Variegated fritillary, I think

And now, what the heck is this? Is it a bee? A bee fly? Something that managed to sneak in from an alternate universe? What???