Spiders have always been part of Halloween superstition since the holiday started in Ireland around the 8th century. One superstition is that if a spider falls into a candle-lit lamp and is burned up by the flame, witches are nearby. Another superstition is if you spot a spider on Halloween, it means that the spirit of a deceased loved one is watching over you.

https://www.livescience.com/16677-halloween-superstitions-traditions.html