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Mayfly Species Epeorus vitreus (Sulphur)

Pictures Below
This is the second most common Epeorus species in the East and Midwest. Most anglers will encounter sporadic hatches of Epeorus vitreus once in a while, and sometimes a more concentrated emergence causes a good rise of fish.  

Where & When


Regions: East, Midwest

Time Of Year (?): Mid-May through early September, peaking in May-June

This Midwestern hatch of Epeorus vitreus is a week or two behind the Eastern emergence.

I believe I encountered a fishable hatch of this species in the Catskills in early September, but I could not positively identify the flies.

Hatching Behavior


Time Of Day (?): Late afternoon and evening, peaking at dusk

Habitat: Riffles

Epeorus vitreus emerges underwater. The duns reportedly leave their nymphal shucks (
Here's an underwater view of the pupal shucks of several already-emerged Brachycentrus numerosus caddisflies.
Here's an underwater view of the pupal shucks of several already-emerged Brachycentrus numerosus caddisflies.
Shuck: The shed exoskeleton left over when an insect molts into its next stage or instar. Most often it describes the last nymphal or pupal skin exited during emergence into a winged adult.
)
while rising to the surface rather than on the bottom.

Spinner Behavior


Time Of Day: Early evening; later on hot days

Habitat: Riffles
The females oviposit by flying low over the water and repeatedly dipping their abdomens in and out. When they're done, they fall spent (Spent: The wing position of many aquatic insects when they fall on the water after mating. The wings of both sides lay flat on the water. The word may be used to describe insects with their wings in that position, as well as the position itself.) with the males.

Nymph Biology


Current Speed: Medium to fast

Substrate: Boulders and gravel

These mayflies survive under a wider range of conditions than Epeorus pleuralis, but they do require a rock or gravel bottom. They do best in fast water.

Epeorus vitreus Fly Fishing Tips


At a distance, this species is easily mistaken for other Sulphur species like Ephemerella invaria by the untrained eye who does not look beyond size and color. This is one more reason to quickly collect a dun if you're having trouble matching a Sulphur hatch.

Pictures of 15 Mayfly Specimens in the Species Epeorus vitreus:

Specimen Page:123
Male Epeorus vitreus (Sulphur) Mayfly DunMale Epeorus vitreus (Sulphur) Mayfly Dun View 4 PicturesThis is my favorite mayfly from 2004, and it appears on my popular Be the Trout: Eat Mayflies products. Check them out!

Its identification is really up in the air. It might be a late-season vitreus dun but it may very well be one of the more obscure species in that genus.
Collected September 2, 2004 from the Beaverkill River in New York
Added to Troutnut.com by Troutnut on January 25, 2006
Specimen Page:123

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