Ephemera danica - Mayfly

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 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 two years 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.

The dun

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.

The spinner

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 mates.

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.

Fishing tip

Trout are sometimes a little wary of large duns that suddenly fall from the sky, so it usually pays to cast well upstream of a rising fish so that your fly drifts across the trout's window in the same way that most of the natural duns will be doing.

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