This is the biggest and best known of the British upwinged flies, and its appearance accounts for great excitement among trout and trout fishers alike. The main hatch usually begins somewhere between mid May and the first week of June, but there are regional variations. The hatch generally begins early in the afternoon and continues for several hours. Emergence of the adults takes place during daylight on the surface of the water or occasionally on a stick, stone or plant stem partially or entirely out of the water.. The males of this species can be found swarming throughout the day, and often swarming continues until dusk.  Once mated, the female flies upstream and descends to the surface of the water to release a few eggs by dipping the tip of her abdomen onto the surface at intervals, or by actually settling on the surface for short periods.  After several visits to the water the egg supply of upto 8300 eggs is finished and the spent female falls on to the surface.

The Nymph:
Living in tunnels in the beds of rivers and lakes, mayfly nymphs have specially adapted breathing filaments which they wave back and forth to create a current over their backs. The body of the male nymph is generally little more than two thirds as long as that of the female.

The developing nymphs, which can grow to over 30 mm long, normally take one year (sometimes two) to reach maturity. They burrow beneath gravel and silt. In spring they emerge from the bed of the lake or river and migrate towards shallower water. They are at their most vulnerable when they begin ascending to the surface to hatch.

Nymphs of this species live in lakes and fast flowing rivers and streams with a sandy or gravely bed.  The nymphs dig into the gravel to form a tubular burrow and they use their specially adapted breathing filaments to create a current over their backs and force the water through the burrow.  The nymphs feed by filtering or collecting fine particulate organic detritus from the water column.  Ephemera danica usually has a two year life cycle, however recent work has shown that in the warmer waters of Southern England it is able to complete its life cycle in one year.  The main flight period is towards the end of May, however adults are often present between April and November.

The Emerger:
The emerger stage is relatively new area of concentration for the fly angler. But it has exploded in popularity, as this stage is the most vulnerable for the mayfly. Not yet an adult and no longer a nymph, they are very clumsy in the water and are free floating as they rise to the surface. Whole groups of patterns have been designed just for this window of a mayflies life. After spending a year or so as a nymph, the mayfly emerges to the surface. On the way, it shucks its outer skin, and pumps fluids into it’s wings. This emerging stage has caught on in popularity in the fly fishing world, as the mayfly emerger is extremely vulnerable. Many mayfly species are clumsy swimmers at best, and combine that with shucking their outer nymph skin, they become a flailing treat for the waiting trout.

The Dun:
Upon emerging they need to dry their wings. There they sit on top of the water, with their sailboat wings upright. The mayfly cannot fold their wings down, which also lend to their visibility for the waiting trout. At this stage they are called ‘duns’. Usually duller in color, they can spend anywhere from a few seconds to a few minutes on top of the water. This is the stage where fly fisherman typically use dry flies to imitate the mayfly. Although each individual insect is only in this stage for a short time, mayflies can emerge by the thousands with the hatches lasting for several hours at a time. It is joy of every fly angler to witness and participate in one of these hatches.

The Spinner:
After drying their wings the mayflies fly to a nearby shrub, tree or bush. Not being very good fliers, their two or three tails, are thought to aid in stabilizing them, though to our eyes they appear like a lot for them to maneuver and carry. Here the duns molt into a second adult phase called spinners. Their second pair of wings now fully developed, they are also sexually mature.

After a few hours or up to a day, they usually, though not always, return to over the water, where they mate. Swarms of male spinners form cloud columns, usually within a stone's throw of the waterside. There they climb and dive until a female flies in to the swarm and chooses their mate. After mating the females lay their eggs, and both male and female die.

Egg-laying mayfly spinners, larger and paler than the males, fly a foot or so above the surface touching down periodically to release a batch of eggs. Once all of their eggs have been expended, the spinners tire and fall to the surface, where they flutter a while before dying in the 'spent gnat' position.

Trout also key on this stage as the ‘spent wing’ spinners give the mayfly one last chance to ‘offer’ itself to the awaiting trout. From our point of view it is hard to deny that the mayfly’s life is nothing but a gift to the wild trout. And the recognition of this fact centuries ago was a gift of one careful observer to the generations of fly fisher’s that have followed.

Written by :

Dan

 

Add comment