Mayflies from the order Ephemeroptera live anywhere from a few hours to a few days as adults depending on the species, with many species living approximately one day after moulting and breeding. In the juvenile stage, mayflies live for months or years in the water, gradually moulting into adults.
The order Ephemeroptera comes from the Greek word ephemeros, which literally means "day long" or "lasting a day." Mayflies are not capable of living longer than a few hours or days because their mouthparts and digestive systems are vestigial or non-functional, meaning that they can never eat and that they die quickly from starvation once they expend energy as adults.
