I was wearing a white t-shirt this weekend and a mason bee landed on my arm. I took that as a sign I should take my cocoons out of the fridge. I waited for a sunny day, placed it on a south-facing ledge and removed the tape from the hole.
Sure enough, a couple of days letter some cocoons were empty and I even saw one tiny eye peeking up at me as I held a cocoon in my hand. I'm pretty sure I saw a couple mating as I was out walking, so maybe some females have emerged as well.
This is an old mason bee house that was given to me. It really should be retired, but I'll give it one last year. I had a class clean and paint these houses to give them the experience. I see they didn't get all the bee poop off the front, but maybe the bees will use the poop designs to help orient themselves to their holes. Shrug. It's a theory.