Atomosia are the diminutive representatives of most eastern robber faunas. There are now just eight species in the genus north of Mexico and most are eastern. Only one is purely western (mucida). This is Atomosia puella. And it is one of the tiniest robbers in our state. Appears even smaller than Megaphorus in flight. Like a tiny fly that likes to land on downed wood and flat surfaces. Without careful observation it can be passed off as a non-robber fly. Norm Lavers gets these all over the gardens in his yard. (Cheryl, of course, found the first ones.) Very active when I saw them and they do cluster and have little flight battles over their perching sites. We have several species of Atomosia documented for the state. And likely several more to go. A surprise species turned up in collections with Jeff Barnes reviewing this genus. It has now been defined as a new species, A. arkansensis Barnes 2008.  A. puella is likely the darkest species and may be the only one here with all dark legs.

One that showed in my own yard. Apparently they love flat surfaces near gardens if they can't have logs. And they perch head down by choice most of the time. Like most of the family, they may oviposit in dead wood.

The same tiny beast with a tiny prey item from Bob's yard in Newton county.

The 2010 version from my yard. A good year for them now that we know how to spot them easily. They love stones and upright barriers in the yard, including brick walls. Seems to have a fruitfly relation as breakfast.

They don't usually take on larger prey. But this front yard, 2019 version certainly took some leggy breakfast. I am guessing a small Cranefly.  
They are everywhere in 2020. When I sit out back with my wife in the improved back yard, they perch on our legs. Guarding against gnats, I suppose. This one was on the front yard wall.   

Atomosia sayii. This is the other more common member of this genus in my neighborhood. It is often found with A. puella. Strangely it often appeared in an open residential area where I lived for several years. It is not common in the woods where I now live. Note the distinctive yellow-orange legs which appear more elongate than the smaller puella. Atomosia rufipes is likely similar but has redder legs and has some dark on the tibias.

The face of sayii. Note that golden color on the upper thorax. A. puella always appears black or slightly greenish in comparison.