I used to think that fireflies and 'lightning bugs' were two different insects, and that 'lightning bugs' were responsible for causing lightning strikes.
A childhood belief about creepy crawlies

others believed things like this
- I believed that lightning bugs were faeries....
::sigh:: I miss those enchanted years of my youth.— Andrea Sorenson - I used to believe electricity came from lightning.Anon
- I used to believe that people could fly during thunder and lightning, because I dreamt this once— Minimania
- I knew lightning could come in through my bedroom window and kill me.
— Cyn - I was convinced that thunder and lightning could wake up volcanos.— leticia
- When I was 10 I thought that if you smoked once God would shoot you with a lightning bolt!— tHOMAS