The wings of the peacock flies are densely patterned. They are held perpendicular to the bodies of the flies and opens and spreads them in an arrhythmic jerking motion, whilst shuffling back and forth. Both males and females perform this dance; perhaps in a courtship which allows for mutual mate choice.
I stumbled onto these strange creatures on the handrail of a nature trail very close to the German/Swiss border. They remind me of Maratus Volans, an Australian jumping spider with a colorful abdomen flap that is used to attract females during courtship.