Do you have Anthophora plumipes or other bees with more colour forms in the area where you live?
In some species of bees, not all individuals look the same but there is some polymorphism. And I don’t mean sexual dimorphism, ie. males looking differently from females, but more than one morph in the same sex. Anthophora plumipes, a common European bee appearing in spring, is one of such species. All males look basically the same but females come in two forms – with brown and black fur. Interestingly, proportions of these two morphs may differ geographically. In Poland where I live, the brown morph is a more common one. In contrast, in UK the black form is more frequent.
Non-honey bees 