What does a butterfly have to do with vampires?
Well not a lot, but they are connected.
In Slavic lore the soul takes the shape of a butterfly when it leaves the body. Not only during death, but also during sleep, and out of body experiences.
The soul can also take the shape of a moth, fly or bird.
When vampire corpses are staked, onlookers watch for the butterfly or moth to escape. If a butterfly is seen it must be captured. The captured butterfly is thrown into a bonfire; this will completely destroy the vampire. If the butterfly escapes, seven years of vengeance awaits the villages.