What's the difference between a butterfly and a moth?

Picture this: you’re outside with a friend, and you both see a little insect flying around. It’s got a small dark body, some tiny antennae, and big colorful wings. You say, “What a beautiful butterfly!” But your friend says, “No, that’s a moth!” How can you tell the difference? We got entomologist Brian Brown to give us the key. If you’ve got a Moment of Um question fluttering around in your brain, send it to us at BrainsOn.org/contact and we’ll try to catch the answer.