What's the difference between a moth and a butterfly?
The best clue is their antennae.
Moths have feather-like antennae with many branches. Butterflies have smooth antennae with a knob at the end.
The feathery antennae above are on an Agreeable Tiger Moth photographed by Chuck Tague. Yes, the moth is agreeing to have his picture taken and yes, that's really his name! Agreeable Tiger Moth (Spilosoma congrua).
The knobs on the antenna below are on a Pearl Cresent butterfly (Phyciodes tharos).
For more differences between moths and butterflies see this vintage article from August 2010: How Do You Know It's a Moth
(photo of Agreeable Tiger Moth by Chuck Tague. photo of Pearl Crescent Butterfly by Kate St. John)