The furry bees may loose more and more hairs as a result of wear during activities like nest building, fighting and mating. They may gradually become almost entirely bold.
Here two males of the Red mason bee (Osmia bicornis syn. Osmia rufa)  in different stages of wear.
This bold male lay dead on the plants underneath the bee hotels.
and a female with parculiar wear damage to the hairs.
References1 Nederlands Soortenregister