possibly from a Cicada nest?

Tony

Cicadas don't have 'nests'. They are very particular on what size branch they deposit eggs and one usually finds their oviposition wounds on lateral branches, unless it was done when the tree was merely a whip. South-facing bark splits can happen with sun scald. Your zone is far removed from my experience as I live in a more temperate area. I can't comment more on that.

I'm pretty sure it's not sun scald as it's about half way under some high shade. I thought maybe woodpeckers made the marks, but I've never seen their damage before. And we have lots of woodpeckers here.