A swarm of bees settling on a roof is an omen that the house will burn down. If a bee enters your home, it's a sign that you will soon have a visitor. If you kill the bee, you will have bad luck, or the visitor will be unpleasant.
Carpenter Bee by Jean Marie (Mouveroux Xylocopa violacea) readily identified by its color. Carpenters bees are about 25 mm, glossy black all over, with sparse black hairs. Taken at Le Perreux sur Marne, Ile-de-France, France.