I saw this movie in junior high school in 1981 on a 16mm projector. It is around 5 minutes long. Black and white. No dialogue. Looks like it was from the 1960s and maybe made in Eastern Europe (Poland?).
Opens on a stark white backdrop. A row of identical workers in heavy protective gear. Their faces cannot be seen. Each one is standing in front of a small machine. In unison, the workers make jerky bowing movements toward the machines. The soundtrack is discordant and suggests loud factory noises.
Suddenly a butterfly appears and begins flying around the workers. One by one, the workers stop working and turn their attention to the butterfly. They remove their head coverings, revealing their faces, and they smile dreamily as the butterfly flits about their heads and hands.
The film ends with a sinister robot overseer pinning the butterfly to a wall in a dark room. The camera pulls back to reveal that this butterfly is but one in a large collection.