My mother believed until very recently, that slugs were snails that had come out of their shells. She used to go around the garden breaking empty shells, so they wouldn't be able to get back in.
A childhood belief about creepy crawlies

others believed things like this
- I used to think shell macaroni was sea shells.— Don Northrup
- If you don't smash egg shells witches use them as boats.— Sarah
- We were told that if you played with egg shells you would get worts !— GAJ
- I used to think that walnut furniture was made out of the shells.— Cambria Consuelo
- I used to think that slugs were just snails who had lost their homes!Anon
- I used to believe that red pistachio shells were the same as women's press on nails.— Bob