They do look close. I found a description of P. acaciae which said it is about 8mm in length, I was thinking yours was a bit smaller? That was a plus with the Acmaeodera, they can be smaller than that. Still looking for the size of P. chamaeleonis. Some of the Buprestidae can be much bigger, so size can be useful for elimination of some that look close, as would be the geographical areas in which they are usually found. In looking for sizes I found this page which might be useful for pictures:
http://texasento.net/TXBuprest...
Do you have a magnifying glass? Sometimes I've managed to get a better picture by pointing the camera lens through one. It looks like hopefully we're in the right family anyway, not sure if we can identify it to species. If anyone here can it would be Janet. Either way it is not a recognized pest of daylilies. I'd have to find the reference again but I think these beetles most likely only have one generation a year so the problem likely won't be ongoing through the season.