As I lazily strolled past a flowering bush in the garden I noticed a small bee land right on top of another and thought it was rather odd. I looked closer and the one on top had the other well and truly pinned and though it tried to squirm out of its grip it was trapped. The squirming got less vigourous as this grip went on for a few minutes (there was enough time to go and get a camera) though I'm not sure how it all ended as they disappeared when I was checking my camera for a good shot.

It didn't look like mating to me (bees mate with birds don't they?) so I assumed it was some sort of predation or parasitism, but actually further research suggests they probably were mating, or at least working up to it. I might even go so far as to suggest that they are a solitary species like a Red mason bee, and that it's a smaller male on top.

Can anyone confirm my interpretation?