(The Birds and the) Bees!

We were sitting under our cherry tree enjoying an al fresco salad lunch when my Editor spotted these bees on a spare chair next to us. I wonder what they were getting up to...?!! Whatever it was it took them over half an hour, and they were quivering the whole time. We were surprised at the size difference - does anyone know which was the male and which the female?

(We're lucky up near the northeast coast - the temperature has been nicely warm but not too hot and judging by the forecast we're not likely to be excessively "sweltered" during the current heatwave.)