Why does the mayfly die so quick?

Mayflies have a short adult lifespan, often lasting just a few hours to a few days, primarily because their primary purpose is reproduction. After emerging from the water, they focus on mating and laying eggs, with their bodies evolved for this specific goal rather than for longevity. Additionally, they do not feed in their adult stage, which limits their energy reserves and contributes to their brief existence. This life cycle strategy allows for rapid population turnover, ensuring the survival of the species.