But it's tricky here...I've pulled out Abbott's book as well as my own images (which he IDed for me a month or so ago.)

However, I think this is a Dusky, and this is the unofficial way I tell them apart (note: unofficial)...as they mature, they pruinose "oppositely" of each other. Duskys are dark above, pale below; Powdered, when younger, are just as dark a blue low on the thorax...and then they get pale on top. We can't really see the face in this image but again, Duskys start out with a pale front of head and darken with age, while Powdered start with a dark head that pruinoses to pale with age. I haven't seen enough of both species through their adult life to know if there's a point at which the patterns "cross over" (each one moving toward its mature coloration) and they look identical.

If this one in life looked almost black from a little distance, then sort of midnight blue, but underlit (the underside of the thorax a cool grey), that would be like the Duskys I saw earlier in the summer. And if it was jittery and difficult to approach to photograph, that's the right behavior.

For a definitive answer, I'd contact Dr. Abbott at UT, perhaps via Odonata Central, which he runs.

I would try the Dancers (Argia).