A scientist from the University of Wisconsin is conducting studies on flies.
He anesthetizes a fly and places it on his lab table. When the fly comes to, he loudly tells the fly to fly away. The fly flies away.
He anesthetizes a second fly, removes one wing, and puts it on the table. When the fly comes to, he loudly tells it to fly away. The fly jumps around a bit, but is unable to fly with only one wing.
He anesthetizes a third fly and removes both wings. When the fly comes to, he loudly tells it to fly away. The fly just sits there.
The scientist writes the following conclusion in his journal:
Removing both wings from a fly makes it deaf.