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Mayfly Genus Epeorus (Little Maryatts)

Taxonomic Navigation -?-
Species in EpeorusNumber of SpecimensNumber of Pictures
Epeorus albertaePink Lady838
Epeorus deceptivus212
Epeorus fragilis00
Epeorus frisoni426
Epeorus grandis214
Epeorus longimanusSlate Brown Dun518
Epeorus pleuralisQuill Gordon542
Epeorus punctatus00
Epeorus suffusus00
Epeorus vitreusSulphur1562

9 species aren't included.
Common Names
Pictures Below
There is remarkable variety of form and color within this prolific genus of fast-water mayflies. Different species are found across the country, and several cause good hatches. Fly anglers are likely to encounter the lesser species on occasion, too.

The best Epeorus hatch in the East is Epeorus pleuralis, the famous Quill Gordon, the first abundant large mayfly hatch of the year. Epeorus vitreus comes a little later and is important in both the East and Midwest.

In the West, Epeorus longimanus dominates in fast, high-altitude streams, while Epeorus albertae inhabits slower and lower waters.

Hatching Behavior

All Epeorus duns emerge from 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.
below the surface, often while still attached to the stream bed. Most species (with the exception of Epeorus pleuralis) take to the air quickly after emerging. These two factors make wet emerger patterns especially effective during Epeorus hatches.

Spinner Behavior

Female Epeorus spinners oviposit by making repeated dips to the surface. They deposit a few eggs, sometimes rest briefly, and then take off for another run.

Nymph Biology

Most Epeorus species require fast, pure water flowing over gravel or boulders. Some can inhabit moderate currents.

Pictures of 52 Mayfly Specimens in the Genus Epeorus:

Specimen Page:1234...6
Male Epeorus (Little Maryatts) Mayfly DunMale Epeorus (Little Maryatts) Mayfly Dun View 12 PicturesI hoped this dun would molt into a spinner for a positive ID, but it didn't. My best guess is Epeorus dulciana, but that's only because that's the smallest western Epeorus species, and this specimen is smaller than any of the others, with a body length of 5.3 mm (although it would be longer as a spinner) and a wing length of 8.5 mm.

It was collected at the same time as a similar-sized female dun.
Collected July 5, 2017 from the South Fork Sauk River in Washington
Added to by Troutnut on July 6, 2017
Male Epeorus (Little Maryatts) Mayfly SpinnerMale Epeorus (Little Maryatts) Mayfly Spinner View 10 PicturesI collected a female dun on the same day that probably belongs to the same species as this spinner.
Collected May 15, 2007 from Enfield Creek in Treman Park in New York
Added to by Troutnut on May 18, 2007
Specimen Page:1234...6

9 Underwater Pictures of Epeorus Mayflies:

Underwater Photo Page:12
In this picture: Mayfly Genus Epeorus (Little Maryatts). From the Mystery Creek # 23 in New York.
Date TakenSep 6, 2006
Date AddedOct 3, 2006
CameraPENTAX Optio WPi
In this picture: Mayfly Genus Epeorus (Little Maryatts) and Mayfly Family Baetidae (Blue-Winged Olives). From Mongaup Creek in New York.
Date TakenApr 19, 2006
Date AddedApr 22, 2006
CameraPENTAX Optio WPi
Underwater Photo Page:12

Recent Discussions of Epeorus

Distance between the eyes of male Epeorus
Posted by Troutnut on May 3, 2007
There has been some discussion here before about Epeorus identification, especially the distance between the eyes of the adult males, which is one identifying characteristic. The keys say that the distance should be "less than the width of the median ocellus," but I have collected a few male duns that didn't quite fit that requirement.

We figured they were Epeorus anyway, so it's not a big deal, but a new specimen I collected sheds a bit of light on the question.

I collected a dun whose eyes were also a bit far apart, which you can see here:

Then it molted into a spinner:

The spinner's eyes were really almost touching, well within the description of the genus. So that answers our question: the duns may have a little wider spread and the gap will close up in the spinners.
ReplySynonym of vitreus 3 Replies »
Posted by GONZO on Oct 4, 2006
Last reply on Oct 4, 2006 by Troutnut
I believe rubidus = vitreus
There is 1 more topic.

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