The male is very nice too (and better for IDing). All of my reference material for this family is at CDFA, so Drs. Hauser or Gaimari will need to put a species name on this one!

Stephen: to me, it is a puzzle why these flies seem to mimic asilids (especially Efferia). For bee & wasp mimicing flies (many asilids, syrphids, etc.), it is obvious that they obtain protection from predators, like birds, that learn to be cautious about attacking stinging prey such as their models. Here ???

I have talked about this with several other people. And I still doubt that these ground loving flies, either Efferia or Apioceridae get much pressure from birds. So the benefits of mimicry must involve a different predator pressure. And does an Efferia mimic get less pressure from Efferia themselves? That would require some direct study. Do lizards and other ground predators shun Efferia because of the large poison sacs and some bad taste effects? Don't know. But I bet Apioceridae are pretty tasty comparatively.

I believe most studies have been done with birds, and we have a fair idea, at least in general, of what birds can see and what they can learn.
But as you suggest, there are many other potential predators, and I'm not sure much is known about whether they can detect the patterns humans see as mimicry, what they can learn or about the state of predation of models and mimics.

It was a happy day when we found this male and female Apiocera. We thought May 6 might be too early because they are recorded out in early June. But we found these two beautiful flies and they cooperated in letting us take their portraits.

Not that I think that evolution should make sense (to us), but now I get it. A non-predator posing as a predator.

Do fly predators avoid Robber flies? Do Robber flies avoid Robber flies?
I've wondered the same thing about syrphids. Who are they fooling? And why does the merest resemblance to a hymenopteran suffice (if it does)? And if it does, why are some syrphids such excellent mimics (to human eyes)?

[Listening to Voyage of the Beagle as an audiobook, and it pushes my mind in such directions.]

imperfect mimicry in Insect Evolutionary Ecology.

I think apiocerids probably look so much like asilids because they are closely related and live in the same arid habitats in which many robber flies live. I doubt there is mimicry.

Thanks for sending the link. The article looks very interesting, but I can't read or download it via my archaic dial-up. So, I will read it on my next visit to the CU library.

I really do think there is mimicry involved in this case. Why is the big question. But the resemblance is too similar. I photographed my first Apiocera in May of 2005 and just automatically put it in with my asilid photos where it remained for about two years. Then, one day I was glancing at the Audubon Field Guide and came across pictures 397 and 398. I said, I have one of those flies. Which is it? And, it turns out I have both, an Efferia (probably albibarbis) and an Apiocera which is the same as #257995 except larger, 24 mm long. Photographs in certain angles do not show the deep depression between the eyes of the robber fly. I first separated them on the basis of Apiocera's more robust abdomen and body length.