This bee is one of my favourites. These are males - smaller, with long antennae and a white moustache. The first in the garden this year emerged on 3rd May, exactly the same day as last year. They then spent nearly three weeks flying around waiting for the females to emerge. The second one below is already looking a bit worn.
On cooler days the males would often sit in the entrances in the bee house, waiting for the weather to improve.
When I first saw this guy I thought he was dead. Then I saw him move and realised he was just resting upside down. A few minutes later he was again looking out of the entrance.
The females eventually emerged in the past week. I was lucky to notice this one starting to chew her way out of her cocoon.
She emerged from the wrong end and had to make a U-turn.
Here she is chewing the cocoon so she can escape and gives a very good view of the scopa (pollen brush) under her abdomen.
There was more chewing to do before she could get out.
Free at last she walked to the entrance and flew immediately, unnoticed by the half dozen males who had been hanging around for days. She flew high in the air, circled a couple of times and was away over the house.
In the past few days the females have been searching for nest holes. These are examining the bee house.
These two show well the two horns on the face used for manipulating the mud used for constructing cells in the nest (hence the name Osmia bicornis).
This one preferred an old screw hole in the wall and spent some time clearing it of cobwebs and spider skins.
I don't think the hole was very deep, perhaps with room for only a couple of cells, and 24 hours later it looked like this, just being sealed up.
This one also preferred the wall. Although most of the holes in the bee house are 8mm in diameter, the bees are happy with holes of only 5 or 6mm in the wall - possibly because they need less mud for each cell. These holes are also shallow so I expect each female would use two or three. The holes in the bee house are 150mm long and it is a life's work for a bee to fill one hole with cells.
I haven't yet been able to get a photo of the bee carrying mud or pollen this year but you can see photos from last year here and the year before here.