They are recognized as being the staple diet of the trout. They are delicate insects with cylindrical bodies and two pairs of erect veined wings. Some mayfly species can be found at almost anytime of the year but others emerge only during certain times between the four month period from May to August. May. This group of fly fishing flies is tied to imitate the natural insects of the order Ephemeroptera. Ephemeros' is Greek for 'lasting a day' and 'pteron' means 'a wing'.
Most adults live less than a day and in some species they survive for only a matter of minutes.
Mayflies do not have any defenses against those that prey on them. What they lack in defense they make up for in numbers. They are an extremely important element of all freshwater fish's diets. There are thousands of fly patterns tied to imitate these insects at the different stages of their development. There is a lot of folklore and fishing jargon surrounding these flies that confuses the beginner.