Q: What bug do knights hate?
A: Dragonflies!

Explanation: Bugs are insects.  A knight (sounds like night) is a soldier for a king or queen.  They often wore armor or a coat of mail and rode on horses.  In stories, knights sometimes fight dragons.

A dragonfly is an insect that eats mosquitoes.  They are beautiful and they do not bite people!

Knights hate dragons but not dragonflies– and that is why this joke is funny!

Here is a video all about dragonflies: