I think that this is a Red Mason Bee O. bicornis (= O. rufa), but I could be wrong. What's throwing me off is how different a solitary bee can look even after a short time. Amazing how fast they "age".
Tech Specs: Canon 70D (F11, 1/250, ISO 100) + a Canon MP-E 65mm macro lens (around 2x) + a diffused MT-24EX (both flash heads on the Canon flash mount) and I had to switch to manual mode (E-TTL metering was getting confused by this scene). These are single, uncropped, frames taken hand held.


Here's the funny part: This is a male Osmia caerulescens, commonly called a Blue Mason bee because of the female's blue abdomen:

I've never seen a female in my yard (LordV, if you're posting here, feel free to add your shot of the girl to this thread). But now that I know they are here I'll look for them. All of the females that have emerged from my cocoons have been Red Mason bees. This male, a week or two from now, won't look the same. The color of his fur won't be as bright, and he'll be missing a lot of it.