This giant-skipper occurs only very locally in SW Texas and northern Mexico. As well, it apparently has a brief Spring flight period--unusual for the Agathymus giant-skippers. My thanks to @upupamartin for helping with the ID and page.

Also known as the Coahuila Giant-Skipper, this species goes by "A. remingtoni" on BG.
https://bugguide.net/node/view/241410