It was one of many beliefs in medieval Europe that witches and devils could transform and take the shape of black cats, according to Phoebe Millerwhite a folklorist and artist “It makes sense that the superstition surrounding crossing a black cat’s paths developed.”

So many myths associate bats with death and darkness. This association comes from the fact that bats are nocturnal animals. Their being nocturnal makes them fit in perfectly in the Halloween culture and theme. The psychical form of bats also makes them fit in. They are like a half-mouse half-bird type of hybrid creature.

The main reason behind spiders being a symbol of Halloween is their connection with witches. Spiders, along with black cats and rats were believed to be evil companions of witches in medieval times.

Rats are associated with bad omens for death and disease. Rats have many connections with Halloween. Rats are sometimes depicted in fiction as being companions for witches, wizards, and warlocks.

Like crows, which are close relatives, ravens have long been viewed as symbols of evil or death. (Think of Edgar Allen Poe’s classically creepy poem, “The Raven.”) Also, carrion eaters and ravens are likewise highly intelligent birds that can learn to mimic other species, including humans.