Who is Mayflies from Joyful Noise: Poems for Two Voices and what is their importance?

Mayflies appear in the poem, Mayflies. They have a life expectancy of one day. They live a frenzied life, trying to fit in as much as possible into the twenty-four hours that are their life. As they lay weakened, their lives come to an end on the same water in which they were born only a few short hours before.