Thanks for the help. We had assumed it was a Bluet, and been browsing them for an hour with no result. We hadn't even considered Dancers. Moving to the guide to represent Texas in July.

We're certain that there is something obvious that we're missing that would tell one right away that you're looking at Argia or Enallagma, but we don't know what it is!!
Several visual clues that we use:
1) Argia usually land on horizontal surfaces and stand horizontally on them - don't forget that's 'Usually'! While Enallagma land on vertical surfaces and hang relatively vertically from them.
2) Argia usually hold their wings folded up above the abdomen. Enallagma usually drop their wings so that they rest alongside the abdomen.
3) Argia usually have a very wide or very narrow black shoulder stripe that often forks at the top in a sort of Y shape. Enallagma usually have a medium black shoulder stripe without the Y fork.
Your image scored 3 for 3 for Argia, so that's where we looked!

information. Thanks so much. I'm a bit embarrassed to admit that we haven't yet purchased a guide to odonata. We obviously need to. But in the meantime, we've actually learned so much from you. Thanks for teaching us.

We've ordered "Dragonflies and Damselflies of Texas and the South-Central United States", and vow to study up!