The Mayfly is in the same family as dragonflies and damselflies. They are known for their very brief lifespan, just a few days, but they spend about a year underwater in their nymph stage. Contrary to popular belief they don't all hatch out in May, but do all hatch out en-mass in each area. Some are known to hatch when the mayflower (hawthorn) blossoms, which may be more appropriate for their name. They are quite distinctive, having three tails. They do vary in size, but these were around an inch long (not including then tails).