I believed if you caught enough fireflies (or "lightning bugs" as we called them in the south), you could light the house with them instead of light bulbs.
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 believed that if you farted too much in a room and you were to light a flame your house would blow up— the nuclear fart
- I used to think light sabers were called life savers.— alison
- i believed that thunder and lightning came out of the alley across the street from my house.Anon
- I used to think that fireflies only came out for the 4th of July. :-)— Whitney
- I use to believe the fireflies were birds with spotlightsAnon