The butterflies fly on the stranger's flower: the flowers on the field path are in bloom, and the butterflies are flying among the flowers.
The butterflies fly in the flowers on the stranger's path, and where has my favorite butterfly flown to?
? This is when the author saw the scene of butterfly blossoms and butterflies flying, he thought of his lover who used to enjoy this scene with him in the past. Here the author expresses his longing for his lover.