The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
In the East and Midwest this is one of the most important hatches of the Spring. They are large flies which emerge sporadically, making for long days of good fishing.
This species contains the two classic Eastern hatches formerly known as Stenonema vicarium and Stenonema fuscum, the "March Brown" and "Gray Fox." Entomologists have discovered that these mayflies belong to the same species, but they still display differences in appearance which the trout notice easily. Anglers should be prepared to imitate both types.
Snagy on Feb 5, 2010February 5th, 2010, 3:32 pm EST
I notice that while the dun, nymph, and spinner photos on the page are all listed as March Brown (maccaffertium vicarium). While the coloration patterns all seem to follow other March Browns I have seen, I notice that the winged flies pictures all have 2 tails, but the nymphs in the photos have 3. I was under the impression this species was a 2 tailed mayfly. Is the nymph mislabelled?
Taxon on Feb 6, 2010February 6th, 2010, 4:01 am EST
Snagy-
Good observation. Maccaffertium vicarium belongs to family Heptageniidae (Flatheaded Mayflies). Heptageniids have three tails as a nymph, and two tails in their winged stages, except for two genera, Epeorus and Ironodes, which have two tails, both as nymphs, and in their winged stages.