A slightly inaccurate title; Andrena agilissima is an oligolectic bee gathering pollen from brassicacaea species.
I let my salad leaves left over from the autumn overgrow and produce flowers. One particular plant produced very large leaves and tall bright yellow flowers.
On the 3.5.14 I saw a bee on the flowers that I had never seen before.
It was a male bee and so was not gathering pollen but the smoky wings and the white hairs made me think of Andrena agilissima.
On the 8.5.14 I was able to get some photographs of a female. The abdomen is smooth and shiny with a metallic, blue tinge and she has once again the smoky wings.
The tufts of white hairs on the sides of the eyes and on the sides of the thorax and the last abdominal tergites are distinctive.
These are mining bees but they nest in communes that can have multiple entrances to a complex of tunnels used by several females. Each female bee will have its own brood cells to lay down its eggs. So a not totally solitary, solitary bee.
They would be very welcome to construct a commune in my garden but so far they have not been frequent visitors.