Mayflies are insects which belong to the Order Ephemeroptera . They have very short lifespan. The lifespan of an adult mayfly can vary from just half an hour to one day depending on the species. The primary function of the adult is reproduction. They have vestigial mouthparts and the digestive system is filled with air. They are aquatic insects whose nymphs called Naiad usually live in freshwater from a few months to an year. The nymphs are a source of food for fish and amphibians. They are close relatives to dragonflies and damselflies (belong to Palaeoptera group of insects). Some other common names of mayflies include Dayfly, Shadfly, Fishfly, Green Bay fly, Lake fly and jinx fly.