European Hornet

Also known as a Giant Hornet. Shows what I know... I thought it was a bee...

I was up early and got a shot of what I thought was a hawk... turns out it was a turkey vulture. Battin' 1000 here. It took looking at the images on the computer to see that ugly scary interesting face and make the identification. I spent the day thinking I had my blip and really didn't photograph too much more. Then this hornet lazily investigated our deck railing. Back and forth, back and forth he wandered, again and again. Well, I couldn't resist... first bee hornet of the season and all. He hung around for tons of shots and didn't seemed bothered that I had my camera up his bum. So, I was able to get a few nice macros and in the end, he bumped the vulture.

Does anyone know what the small "buttons" (for lack of a better word) on the top of his head are?