Source : Webster's Revised Unabridged Dictionary (1913)

Io moth \I"o moth`\ (?; 115). (Zo["o]l.)
   A large and handsome American moth ({Hyperchiria Io}), having
   a large, bright-colored spot on each hind wing, resembling
   the spots on the tail of a peacock. The larva is covered with
   prickly hairs, which sting like nettles.