If any animal has earned notoriety for no reason, like the black cat has, it's the bat. In fact, bats are so ill-famed that they are killed only because people think that they would bring them bad luck. A bat seen in the house is said to be a sign of someone dying, while one seen in the church during a wedding is said to be a bad omen, or a sign of bad marital alliance. Nobody wants bad things to happen to them, but believing that something bad will happen to you just because you saw a bat is definitely uncalled-for.
There do exist superstitions which suggest that bats bring good luck, but it only gets worse as even these superstitions require them to be killed. Bat's blood has long been associated with black magic and witchcraft. While there is no concrete evidence, it is believed that people continue to go by such beliefs. In folk medicine, various parts of the bat's body, including bones, wings, and eyes, are used to cure ailments, like asthma and rheumatism, improve vision, and even to prevent balding. In the past, it was even believed that drinking a bat's blood could make a person invisible.