This female was found actively flitting about on flower heads of Bebbia juncea var. aspera, in the sunflower family, Asteraceae. Periodically another individual, presumably a male, would dash in and chase her about... apparently atttempting to mate. But being unsuccessful in gaining her cooperation, it would then dart off after a few seconds, without ever landing on the flower heads. (Unfortunately, I was unable to photograph him.)

At first, and from a distance, the two seemed bee-like. But a number of subtle cues put that impression in doubt. First off, their flight patterns seemed different: rather vertically "jerky" and erratic...moving more like a fly (or beetle!) than a purposeful bee out collecting pollen or nectar. The female would quickly land on a flower head and then suddenly bob...off it, then back onto it...doing so repeatedly in an agitated "un-bee-like" way. Most tellingly, she kept landing...not with her head and mouthparts directed towards the flowers...but with her rear-end pointed into the flowers, and her head and body oriented downward and away from them! By the time this observation was sinking in on me, I was close enough to notice that the attennae looked unusual...and the realization dawned that these were ripiphorid beetles!

If I had not previously encountered Ripiphorus, I would no doubt have been totally baffled by these strange, bulky, "bees" with moth-like pectinate antennae! But I *had* encountered one once before, and afterwards spent *much* time and effort pondering, studying, and eventually solving what was initially a very vexing riddle...namely: "What in the world were these things?"!!

This time was different though. The first time I had come across a totally torpid female during a cool, windy, late afternoon...tenaciously clasping the flower head of a native mint. There were no other individuals, and basically no active behavior. So this time it was a thrill to both know what I was seeing, and observe the interesting behavior of both a male and a female.

As far as the ID goes, alas, Ripiphorus can be very difficult to get to species...and in fact it's a genus where the taxonomy is somewhat in disarray and in need of a revision. In the field, I immediately had the hunch this was Ripiphorus rex...and after studying all my (unfortunately not-so-good) photos...I was eventually able to discern all the characters necessary to convince myself of that (i.e. the very obliquely truncate hind basitarsus; the subtle "nub-like" serrations along the anterior edge of the mid-tibia (most noticeable on the apical end); the hairy, conical projection between the bases of the forelegs; etc.). All these aspects of the species ID...as well as much detail and support for the synonymy of R. "vierecki" under R. rex...appear within copious(!!!) remarks and comments scattered among the posts below:

     

...and in this BugGuide forum topic.