The folklore behind popular bat Halloween decorations
Bats are a nearly ubiquitous decoration for Halloween. Their popular association with vampires as a form that the undead blood drinkers can take accounts for the bat being a motif of Halloween.
In addition to the vampire connection, bats tend to stir feelings of horror and revulsion among most people. The flying rodent's lack of good looks makes them worthy of cringe-inducing décor. Most people consider bats downright repulsive. Add to their resume their nocturnal nature and a species that sucks blood, and bats are a natural choice for adding creepy flair to Halloween decorations.
Folklore, especially from the Isle of Man, also links bats with witches that are said to be capable of taking the form of bats and flying. In Scotland, old beliefs declare that the witches' hour has come when bats fly upward into the night and swoop swiftly back down to Earth. Bats are also associated with death omens, and their susceptibility to rabies builds a real connection with disease that increases their yuck factor.
The natural behavior of bats has assigned them to horror show menagerie. Their night flights automatically make them a symbol of the fearful unknown, and their habit of hanging upside down to sleep just makes them a little weird to the sensibilities of most people.
For the most part, bats are harmless creatures that eat mosquitoes or pollinate fruit. Even so, bat replicas will surely continue to serve as Halloween decorations because they freak most people out.