Samhain, the Irish and the Celtics
Some speculate that the Celtics were the first to bring the harvest celebration of Samhain to Ireland. However, Irish literature that predates the arrivals of the Celts by several hundred years mentions the festival. Druids in Ireland spend centuries building large bonfires celebrating the harvest season and trying to communicate with spirits. Some bats eat thousands of bugs each night because they are nocturnal animals, and sometimes more if they are getting ready for hibernation. Samhain fell during the same time that Halloween does on our modern calendar. Not only are the two holidays linked and similar, but they coincide with the month leading up to bat hibernation season. If Irish druids built big bonfires, bugs were very likely also to attend the festivities. Bats came to do what they do best: rid the world of bugs. Except, the Irish and later even the Celts had no idea what bats were or what they were doing as they dove in and out of the firelight making high-pitched noises. We now know that bats are efficient bug eaters with echolocation, not human superpredators or evil winged creatures. Even bats that are sanguivorous prefer the blood of goats and birds to humans. Regardless, as a result, bats were associated with unwelcomed spirits with harmful intentions, a misnomer that would follow them for thousands of years.