When I was a kid my dad ground up fruit flies to get at their imaginal discs, which were involved with development of the legs and wings in the adults. I tried to get him to explain this once, and ended up convinced that they were "imaginary" discs (I asked what they looked like, and he said you couldn't see them). For years I couldn't understand the point of grinding them up.
A childhood belief about creepy crawlies

others believed things like this
- When I was younger I thought the disc holder for our TV would explode if you put too many discs in. Anon
- I thought buffalo wings were wings from a buffalo, for years I looked for their wingsAnon
- a friend was convinced that his school was an asylum, and couldn't be convinced otherwiseAnon
- I used to think that boysenberry was poisonberry and couldn't understand whay anyone would want to eat it.Anon
- I could NOT understand why, if a pen worked on paper, it couldn't also write in thin air.— Can you guess what it is yet?
- When I was little, I couldn't understand why people called me a tomBOY, instead of a tomGIRL.— Amanda