The third Pompylid wasp mimic after the two Pogonosoma species in Arkansas is the robber fly Orthogonis stygia. It is exceedingly rare and previously one of the Holy Grail robber flies. Before this summer (2004) only about six females were known from North Carolina, Florida, Texas, Mississippi and Arkansas. Some fieldworkers in Texas caught a female in 2002. Before that Bromley caught the last one in 1950.

The males were unknown to anyone. The above shot taken by Norm Lavers replaces his prior shot which was the only shot of the male on the planet. An image of a similar Japanese specimen is here. They lack the white facial hair and have a blunter proboscis than the Pogonosoma. The wing veins are distinctly different. They lack the cross vein of Pogonosoma among other features. Norm caught a male of this species on 8 July 2004 in Clay county, Arkansas (the prior Arkansas record was from Washington county). That is the first male ever taken anywhere. It was inhabiting this very same log as shown in the shot below. A second male came to replace it and Norm observed it over several separate visits (see also below), sparing this guy.

Since these findings in the Crowley's Ridge counties of Arkansas, they have been located in several other southern states. Including multiple in LA as well as KY, GA, VA and most recently SC (in 2022).

Shot from above of the same male. You can almost see the parallel veins on the outer wing.

The specimen shot from Norm of the male. His observations quoted from the second visit.

"We watched it for about two hours and I made notes.  Here is the gist.  Since there was a new male on the log, we decided either they were serially emerging from that log (we didn't find any pupal cases) or, it was such a perfect habitat, as soon as it was available, a waiting male took it over.  So here was the setting.  The log was a well rotted fallen oak, about 18 inches in diameter, and about 40 feet long.  It was in woods with dappled sunlight, the understory bare, fallen leaves, occasional tree (oak) seedlings or saplings, on an eastward-facing slope of about 30 degrees, near the top of a ridge which was a high bluff over the St. Francis River, which there (Chalk Bluff, Clay County) comes together with Crowley's Ridge, and marks the NE border of Arkansas and Missouri.  The soil was loess, common along Crowley's Ridge. 

"It landed occasionally on the leaf litter, usually picking a fresh leaf to land on, and occasionally on a leaf of a seedling oak a few inches off the ground, but 90% or more of the time it landed on the trunk of the tree.  It landed indifferently in sun or shade, very frustratingly for me trying to photograph it.  It would let me come within about five feet of it, then fly away five or ten feet.  But no matter how many times I annoyed it, it would not leave the log.  Sometimes it landed facing me, aware of my presence, but at other times it circled towards me, once landing on my pant leg.  When we first came it had a small insect, which proved to be a small (6-7 mm) ichneumon with a bright red abdomen, a species common in woodland.  Once a male Promachus bastardii came by, but there was no interaction.  The log was also possessed by a Laphria grossa, which however did not land on the log but landed on the leaves of sapling oaks right beside the log.  There was no interaction between the two except once when the Orthogonis flew by the Laphria, it flew up then, though I couldn't tell if it had predation in mind, or defense of its log.  They flew rapidly around each other twice from a distance of 2-3 inches, then separated, the Laphria landing on its leaf, the Orthogonis on the log.  From close up, the Orthogonis made a low buzz in flight.  At one point Cheryl saw him taking a bath, during which he seemed to flex a part of his tail-end apparatus. My guess is, it waits on the log for females, but we didn't see any."