Fred First, of Fragments from Floyd, over in Floyd County, Virginia, has been troubled by a Bully Bee on his white butterfly bush. In turn, I have been troubled by my inability to identify this creature. Fred's observation of the Bully Bee killing a skipper convinced him that it was a predaceous wasp.
Of course, I thought. A sphecoid of some sort, or a big vespoid, provisioning its nest with live but paralyzed prey for the wasp larvae to eat. These are wonderful creatures. As a child, I spent hours watching black-winged orange wasps provisioning their burrows with caterpillars, and when I lived in Our Nation's Capital, I was delighted to see and hear cicada killers at work.
Yet something seemed wrong. Most of these predaceous wasps specialize in particular types of prey. Some only feed their offspring spiders. Some only prey on bees. I'd never heard of any that went for adult lepidopterans, and none of them sit on branches, devouring their prey. Was Fred mistaken about this? Then it dawned on me. Robber flies. Ferocious, indiscriminate predators. There are some big ones here in Pocahontas County, and I've mistaken them for hymenopterans more than once.
So, that's my latest identification of this insect I've not seen or heard. If I'm right, I'm going to hang out a shingle as "Psychic Entomologist of the Blogosphere."