Morpho butterflies have ears on their wings

Scientists thought butterflies were deaf until 1912 when the first butterfly ears were identified. Only in the past decade or so have researchers examined the anatomy and physiology of butterfly ears, which they are finding to be quite diverse and present in several butterfly species.

The latest discovery was made with the blue morpho butterfly (Morpho peleides), which dazzles with its bright-blue wing coloration when it flits about in its native Central and South America... In the new study, Kathleen Lucas of the University of Bristol in England and her colleagues were interested in the odd-looking hearing membrane that sits at the base of the blue morpho's wing. The tympanal membrane, as it is called, is oval-shaped with a dome at its center that kind of resembles the yolk at the center of a fried egg, Lucas said...

Taken together, the vibrational and nerve recordings suggest this butterfly can distinguish between different pitches, though further research is needed to confirm this ability.  

Text from Live Science (more info there and at the J. Exp. Biol. publication).  Photo via animals, animals, animals (original source uncredited).  A macro view of the ear structure is posted at MSNBC.