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Mayfly Genus Epeorus (Little Maryatts)

Taxonomic Navigation -?-
Species in EpeorusNumber of SpecimensNumber of Pictures
Epeorus albertaePink Lady730
Epeorus deceptivus18
Epeorus fragilis00
Epeorus frisoni426
Epeorus grandis214
Epeorus longimanusSlate Brown Dun35
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 47 Mayfly Specimens in the Genus Epeorus:

Specimen Page:1234...6
Male Epeorus frisoni Mayfly DunMale Epeorus frisoni  Mayfly Dun View 9 PicturesI collected this male dun together with a female spinner, a female dun, and another male dun.
Collected September 6, 2006 from Mystery Creek #23 in New York
Added to by Troutnut on October 3, 2006
Male Epeorus pleuralis (Quill Gordon) Mayfly SpinnerMale Epeorus pleuralis (Quill Gordon) Mayfly Spinner View 10 PicturesI 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.) most of the day looking for Epeorus pluralis duns or spinners without any luck on the major Catskill rivers. Finally in the evening I arrived at a small stream somebody had recommended, and when I got out of the car I was happy to find that I had parked in the middle of a cloud of male spinners.
Collected April 19, 2006 from Mongaup Creek in New York
Added to by Troutnut on April 22, 2006
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

Just wondering about this one Epeorus larval 6 Replies »
Posted by Brookyman on Jan 15, 2013 in the species Epeorus deceptivus
Last reply on Jan 16, 2013 by Brookyman
Hey everybody I just did a color illustration of Epeorus longimanus based on a sample from the biodiversity group collection @ the university of Guelph. This one bares a big resemblance to that sample.
This one seems more transperent but it is a living sample, and the ones on the site are in preservative.
The median posterial terga bands and the head capsule shape is what made me think this maybe E. longimanus.

Just wondering if this is E. longimanus and if so can it be label it as such ???

Here is the sample I worked off of.

ReplyDistance 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

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