Adult mayflies have no functional mouths. Then how do they eat, you wonder? Adult mayflies never eat and, as a result, die of malnutrition. They live for a brief span, from a few hours to a day, during which they mate. Indicators of clean, healthy waterways, mayflies eat only during their larval stage. The adults of some species live as few as two hours, which doesn’t give them very much time to do all their reproduction business, but such is life for a mayfly.
Mayflies “hatch” (emerge as adults) from spring to autumn, not necessarily in May, in enormous numbers. Some hatches attract tourists. Fly fishermen make use of mayfly hatches by choosing artificial fishing flies that resemble them. One of the most famous English mayflies is Rhithrogena germanica, the fisherman’s “March brown mayfly”. Like a lot of other insects, mayflies cycle through different metamorphic stages during their lives — think of them as insect costume changes. The first two take place in the water as an egg and then a larva. After hatching, a mayfly larva feeds, grows and develops, some males building burrows to live in and feed from, while others just cruise around in the aquatic vegetation, finding snacks. During this time, they grow and molt over and over — as many as 50 times for some species.
Credit : How stuff works
Picture Credit : Google
