They're in Idaho, knocking on the doors, wanting to move in with their extended families.

I've always thought that we associated spiders and Hallowe'en for several reasons:

1. Many people are frightened of spiders.
2. You find lots of spiders in uninhabited buildings.
3. "Haunted houses" are usually uninhabitated and hence have spiders.
4. There's a vampiric element to the way spiders feed.
5. Some spider venom can sicken and even kill you.