On this map you see where there were observations of Mayflies around the world. This will give you an idea of the global distribution of this class. Note that a class can have many different families, and thousands of species.
Years 2000 until now, source: GBIF
There are over 3,000 known species of mayflies belonging to 42 families and approximately 400 genera within the Ephemeroptera class. Mayflies can be found in various countries around the world, inhabiting every continent except Antarctica. They thrive in a wide range of freshwater habitats such as streams, rivers, and lakes.
The life cycle of mayflies consists of four stages: egg, nymph, subimago, and imago. The female mayfly deposits her eggs in water, which then sink to the bottom or attach to underwater vegetation. After hatching, the nymphs spend most of their lives underwater, feeding on algae and other organic material.
Nymphs go through several molts before becoming subimagos, the penultimate stage in their life cycle. The subimago stage is unique to Ephemeroptera and is characterized by a sexually immature adult form with duller colors and less developed wings. Subimagos eventually molt one final time to become fully mature, sexually active adult mayflies, known as imagos.
The adult mayfly stage is short-lived, lasting only a few hours to a couple of days. During this time, mayflies focus solely on reproducing. After mating, females return to the water to lay their eggs, and both males and females die shortly after. This brief lifespan has earned mayflies the name "Ephemeroptera," which comes from the Greek words for "short-lived" and "winged."
Mayflies play a crucial role in fly fishing due to their abundance and the feeding habits of fish such as trout and salmon. Fishermen closely observe mayfly hatches to predict the best times to cast their lines, as fish are more likely to feed during these periods.
"Matching the hatch" is a fundamental concept in fly fishing that refers to selecting an artificial fly that closely resembles the natural insects fish are feeding on at a given time. By closely observing mayfly hatches and their life stages, fly fishers can choose the most suitable artificial fly to imitate the natural prey, increasing their chances of success.
While you read most about fly fishing trout on the dry mayfly pattern, which is the adult and final stage of the mayfly, it's important to know that mayflies actually spend most of their lives as nymphs. So make sure you have a wide range of their nymph stage available in your fly box as well.
There can be thousands of species within an order, and therefore lots of different flies imitating various of these species. Flies can also imitate different stages, for example larvae, pupae and adults.
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Each order has an indication of its relevance to fly fishing:
= Not so relevant
= Somewhat relevant
= Most relevant
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