Yellow Angled Sulfa/Sulpher butterfly
I don't have a picture but am sure I watched the above butterfly on our lantana this morning. I am in Bastrop, TX. The photos of said butterfly that I found on-line all place it in Hidalgo County or deep south Texas. Is it unusual to see one this far north and in east TX? I'll keep an eye out and try to photograph it next time I see it if it's a rare thing -- maybe it's migrating?? I always appreciate your answering my myriad questions!!
Bastrop County Texas
There are about 30+ species of Pyridae butterflies (sulfurs) that occur in Texas, so it's most likely a pretty common one to your area.
There are some species that are more specific to the Rio Grade Valley, but without seeing a picture of it, its hard to know if that's the species or another more common one.
Here's a link on the A&M field guide website with a little more information about sulfur butterflies for you.