The mayfly, of the genus Ephemera, and its best known and most abundant species on European rivers, danica and vulgata, are an important part of the diet of trout and grayling, usually from mid-May to mid-June. It is not uncommon to see mayflies on the water later in the summer, but they are not of the same interest to salmonids.
Ephemeridae are not among the families of mayflies most impacted by the degradation of aquatic environments, so their emergence can be massive, even in slightly degraded rivers.
The massive emergence (hatch) of Ephemera danica, the most widespread, is a great moment for the fly fisherman as it marks one of the most beautiful periods of the season for dry fly fishing, as trout are actively looking for these insects, at all stages of their metamorphosis.
It should be noted that depending on the type of river or lake, the physico-chemistry of the water determines the size of the insects: the May flies of the chalky rivers of Normandy, the Franche-Comté region or the south of England or of certain Irish lakes are much larger than those of the rivers of the Armorican massif or those with slightly acidic water.
This is one of the times of the year when the best trout come to the surface and reveal their presence. It is therefore an opportunity to observe and often to try your luck on big fish which may then lose some of their wariness.
If you have the choice, and if you live near the river, the first two weeks of emergence are the most favourable because afterwards, the fish learn quickly to make the difference between natural and artificial.
I offer you a complete selection of effective imitations of mayflies, whatever the stage the fish are interested in, because everything is not always simple, as massive hatchings mean fish that are sometimes stuffed or full and therefore fussy.
The wet, stillborn, cripple, emerging or spent stages are sometimes preferred to the subimago (dun) and imago (spinner) stages.
In order to be able to deal with all situations, one cannot be satisfied with a few imitations of subimagos (duns).
It is absolutely necessary to consider the emergent stage and its variants and the spent stage.
My selection includes the best of Fulling Mill, Devaux and McPhillips.
It is focused on river fishing, but I also offer the best nymphs, wet flies and dry flies for fishing on Irish lakes, one of the most important places for Mayfly fishing in Europe.
Some of these patterns are also very effective in rivers.
