Osmia bicornis, or Red Mason Bees, are solitary bees. You can find these bees in the holes in walls and timber, or sometimes they'll choose the hollowed-out stems of plants. A female will build her nests using mud. They use this to mould individual chambers, in which they lay one egg on a ball of sticky pollen. If you look closely, you can sometimes see females carrying pellets of mud back to nesting sites. These bees are particularly fond of flowering fruit trees. O. bicornis is a docile bee and reluctant to sting.