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Mayfly Genus Ephemerella (Hendricksons, Sulphurs, PMDs)

Taxonomic Navigation -?-
Species in EphemerellaNumber of SpecimensNumber of Pictures
Ephemerella aurivillii00
Ephemerella dorothea dorotheaPale Evening Dun00
Ephemerella dorothea infrequensPale Morning Dun00
Ephemerella excruciansPale Morning Dun00
Ephemerella invariaSulphur Dun015
Ephemerella needhamiLittle Dark Hendrickson00
Ephemerella subvariaHendrickson024
Ephemerella tibialisLittle Western Dark Hendrickson00

11 species aren't included.
Common Name
Pictures Below
This genus contains the legendary Hendricksons and Sulphurs of the East and the equally important Pale Morning Duns of western waters.

No scientific name in American angling literature is more renowned and at the same time capable of more confusion than the genus name "Ephemerella." It is important that anglers have a good overall grasp of its taxonomic history if they are to make any sense out of the rich literary heritage involving this mayfly name.

By the time American angling literature began to take serious note of entomology in the decades of the early to mid 20th century, Ephemerella was considered a "super-genus" in the family Baetidae, containing all of the important species to anglers in the subfamily Ephemerellinae. Taxonomists organized them by association with "type" species that were referred to as "groups" within this very large and unruly genus.

This organizational structure held sway until the 70's when they were recognized as separate from the Baetidae with their own family, the Ephemerellidae. The "groups" (after a little name changing and reorganization) were given subgenus status, but in conformance with taxonomical convention,the nomenclature retained the use of the name Ephemerella when referring to individual species genus status. More change occurred towards the end of the century as consensus formed around the subgenera achieving full generic status. The broad use of Ephemerella was then dropped in favor of the new generic names.

These changes were necessary in that they addressed many problems exposed in older taxonomies. Unfortunately, all during this period the changes were reported with varying degrees of accuracy and acceptance. For anglers this was exacerbated by the continued use and reliance on older entomology texts in many circles. Be that as it may, recent or updated angler entomologies now recognize that many of the old Ephemerella species are spread out among several genera in the Ephemerellidae family. These include the various Blue-Winged Olives and Western Green Drakes of the Drunella genus as well as several important species scattered in genera like Attenella and Serratella, to name a few.

Despite these revisions in classification, the Ephemerella genus still contains arguably the most important species in North America, and remains a "super-genus" to anglers.

There is a lot of variation; refer to the genus species hatch pages for details.
  

Where & When


Regions: East, Midwest, West

Time Of Year (?): Mostly in the spring in the East, all season in the West

Ephemerella species inhabit most types of water and can be found at any time of the season depending on locale. This genus is very important in the East and Midwest, where the major species hatch in the spring and a few continue into the summer. In the West, the species comprising the Pale Morning Dun complex produce the superhatches of international fame that can be found somewhere in this vast region virtually the entire season.

Hatching Behavior


Variable - see species

Spinner Behavior


Time Of Day: Evenings in the East, mid-mornings in the West (with exceptions)

Habitat: Riffles if available, otherwise specific locations based on several considerations.
The concentrated evening spinner falls of many species in this genus are some of the best fly-fishing events of the spring in the East. In the West, many mid-morning spinner falls have achieved legendary status.

They are also one of the groups of mayflies prone to the unfortunate behavior of mating and ovipositing over blacktop roads hundreds of yards from the river.


Pictures of 158 Mayfly Specimens in the Genus Ephemerella:

Specimen Page:1234...17
Male Ephemerella subvaria (Hendrickson) Mayfly DunMale Ephemerella subvaria (Hendrickson) Mayfly Dun View 9 PicturesI collected this male Hendrickson dun and a female in the pool on the Beaverkill where the popular Hendrickson pattern was first created. He is descended from mayfly royalty.
Collected April 19, 2006 from the Beaverkill River in New York
Added to Troutnut.com by Troutnut on April 22, 2006
Male Ephemerella aurivillii Mayfly SpinnerMale Ephemerella aurivillii  Mayfly Spinner View 15 PicturesThis spinner molted from a dun after being photographed, and the dun form is listed here as a separate specimen. I've rarely found a more cooperative and photogenic mayfly.
Collected July 10, 2011 from Nome Creek in Alaska
Added to Troutnut.com by Troutnut on July 16, 2011
Male Ephemerella subvaria (Hendrickson) Mayfly SpinnerMale Ephemerella subvaria (Hendrickson) Mayfly Spinner View 11 PicturesI collected this beautiful male Hendrickson specimen as a dun, along with a female Hendrickson from the same hatch. Both molted into spinners in my house within a couple of days.
Collected April 23, 2007 from Fall Creek in New York
Added to Troutnut.com by Troutnut on April 25, 2007
Specimen Page:1234...17

37 Underwater Pictures of Ephemerella Mayflies:

Underwater Photo Page:12345
This is a close-up underwater view of a stillborn Ephemerella subvaria (Henrickson) female dun.  In this picture: Mayfly Species Ephemerella subvaria (Hendrickson). From the East Branch of the Delaware River in New York.
This is a close-up underwater view of a stillborn (
This stillborn Ephemerella subvaria dun is trapped in its shuck.
This stillborn Ephemerella subvaria dun is trapped in its shuck.
Stillborn: In fly fishing, a stillborn insect is one which got stuck in its nymphal or pupal shuck during emergence and floats helplessly on the surface instead of flying away. It is a specific class of cripple, although it is sometimes used interchangeably with that term.
)
Ephemerella subvaria (Henrickson) female dun.

In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
Date TakenApr 19, 2006
Date AddedApr 22, 2006
AuthorTroutnut
CameraPENTAX Optio WPi
This picture from below shows a stillborn Ephemerella subvaria (Hendrickson) dun drifting on the surface amidst a number of shed pupal skins from Brachycentrus caddisflies which were heavily hatching that day.  In this picture: Mayfly Species Ephemerella subvaria (Hendrickson) and Caddisfly Species Brachycentrus appalachia (Apple Caddis). From the East Branch of the Delaware River in New York.
This picture from below shows a stillborn (
This stillborn Ephemerella subvaria dun is trapped in its shuck.
This stillborn Ephemerella subvaria dun is trapped in its shuck.
Stillborn: In fly fishing, a stillborn insect is one which got stuck in its nymphal or pupal shuck during emergence and floats helplessly on the surface instead of flying away. It is a specific class of cripple, although it is sometimes used interchangeably with that term.
)
Ephemerella subvaria (Hendrickson) dun drifting on the surface amidst a number of shed pupal skins from Brachycentrus caddisflies which were heavily hatching that day.

In this picture: Mayfly Species Ephemerella subvaria (Hendrickson) and Caddisfly Species Brachycentrus appalachia (Apple Caddis).
Date TakenApr 19, 2006
Date AddedApr 22, 2006
AuthorTroutnut
CameraPENTAX Optio WPi
Underwater Photo Page:12345

Recent Discussions of Ephemerella

PMD Spinner - Egg sack color? 20 Replies »
Posted by Wbranch on Jan 26, 2010 in the species Ephemerella excrucians
Last reply on Aug 18, 2020 by Troutnut
Do any of you entomologist types know the true color of the PMD spinner? Dorothea or excrucians. Where I fish in MT there are huge spinner falls, many spents are on the water in the morning and others fall again at various periods during the day. I'd like to tie some with egg sacks as I saw many in July but forgot what color they were. Thanks.
Replyrotunda 8 Replies »
Posted by CharlieBugs on Jan 26, 2015 in the species Ephemerella invaria
Last reply on Feb 1, 2015 by Gutcutter
Your post on Ephemerella subvaria brought back some memories that might be of interest to some readers.
I got my master’s degree under Ed Cooper at Penn State in 1966. I studied the impact of low oxygen from Penn State’s sewage plant on the mayflies of Spring Creek. The plant mostly removed BOD (organic matter which causes low oxygen) by oxidizing it in a bacteria rich environment. But at that time the plant did not remove phosphorus (and nitrogen) which fertilized the macrophytic algae and other plant growth. There were far more macrophytes (large plants) in Spring Creek below the sewage plant entrance than above, and essentially no mayflies. What was there in the effluent that killed the mayflies? Mayflies put directly in the effluent did not die over a 16 hour day. But oxygen samples taken over 24 hours in summer showed a much greater variation below the effluent (from 16 ppm (or mg/l), 160% of saturation in late afternoon) to 3 ppm (30 percent saturation just before dawn) (vs 14 to 10 ppm, +- 20 percent saturation above the effluent.
I built a Rube Goldberg machine in the lab that would control the oxygen levels and temperature of control and experimental cages that each held 25 mayflies. The control would keep oxygen near saturation and the experimental one would lower the oxygen over 8 hours (the length of night in summer). Mortality was dependent upon both oxygen level and temperature. Virtually no mayflies would die if the oxygen was above 2 PPM (or mg/l) at 8 C, or at 4.5 at 20 C. Seventy five percent of larvae would die at 1 ppm at 8 degrees and 2.5 ppm at 20 degrees. So the mortality was much more if the temperatures were high. Hence most of the mortality would presumably occur in August when the high temperatures (20C) would increase the larvae metabolism and hence need for oxygen, but the water would hold less oxygen even before the night-time respiration of the macrophytes would reduce it much further (to only 3 ppm). Thus the low nighttime oxygen caused by excessive plant growth was a sufficient cause or the near total absence of mayflies below the sewage plant. Recognizing the aquatic impact Penn State started to use land disposal of its effluent which as far as I knew alleviated, and even stopped, the negative impacts on the mayflies. Can anyone verify this ? The otherwise well done “The Fishery of Spring Creek; A Watershed Under Siege “
By Robert F. Carline, Rebecca L. Dunlap Jason E. Detar, Bruce A. Hollender Has nothing on dissolved oxygen or aquatic insects. In my opinion we need much more of an ecosystems approach for streams (Which we are doing for Little Sandy Creek in N.Y.).


Now back to Ephemeralla subvaria. The title of the paper I published on this project (my first of nearly 300 publications) was:
1. Hall, C.A.S. 1969. Mortality of the mayfly nymph, Ephemerella rotunda, at low dissolved oxygen concentrations. J. Elisha Mitchell Sci. Soc. 85(1): 34-39 (M.S. Thesis, Pennsylvania State University, 1966).

Whoa! Ephemeralla rotunda? This was by far the most abundant mayfly in Spring Creek where I sampled! But I could not even find the name in your list. Also I had my samples verified by Burke, author of the authoritative "Mayflies of Illinois", and he said Well that’s what it keyed out to in my book”. (Talk about scientific ass covering! ) Well to make matters worse (as of 24 hours ago) my next girlfriend, Molly, at the University of North Carolina, loved the name of “Ephemerella rotunda”, the rotund one, which comes to think of it described her as well. I liked it too. But n’exist plus: where had the most abundant mayfly gone? Fortunately upon reading the rest of the post I found “Ephemerella invaria is one of the two species frequently known as Sulphurs (the other is Ephemerella dorothea). There used to be a third, Ephemerella rotunda, but entomologists recently discovered that invaria and rotunda are a single species with an incredible range of individual variation." Ahh neither rotunda nor Molly stood the test of time. So I assume what I called rotunda is still alive and well in Spring Creek as invaria. Again, can anyone verify that?

If anyone wants to follow up on the distribution and abundance of mayfly (or any other species) may I recommend: Hall, C.A.S., J.A. Stanford and R. Hauer. 1992. The distribution and abundance of organisms as a consequence of energy balances along multiple environmental gradients. Oikos 65: 377-390. I can send it if you cannot get it from google, which I think you can. (chall@esf.edu)
ReplySo is Ep Infrequens now known as Ep Dorothea? 20 Replies »
Posted by Wbranch on Feb 17, 2008 in the species Ephemerella dorothea infrequens
Last reply on Jul 1, 2014 by Crepuscular
These mayflies look more like the Sulfurs I see on the Delaware system than the PMD's I see in Montana. The Montana mayfly has a distinct yellow leading edge to an overall light dun gray wing and the abdomen and thorax have a more light greenish/yellow cloration so how is it that Infrequens is now known as Ep Dorothea Dorothea?
ReplyInvaria - Dorothea confusion 17 Replies »
Posted by Entoman on Feb 1, 2012
Last reply on Feb 7, 2012 by Entoman
The following is from an older post of Gonzo's.

It's been my suspicion for quite some time that a good part of the credit given to dorothea for creating the later, lighter-colored "little sulphur" hatch should probably go to the same species (or species complex) that creates the earlier, larger, darker hatch--E. invaria. Many anglers who fish the small suphurs on valley limestone streams in my home state believe (or have been led to believe) that they are fishing the dorothea hatch. Close inspection of the mayfly that causes the activity usually doesn't bear that out. Most of the true dorothea hatches seem to come from mountainous areas where the streams are faster and have rockier bottoms.

All of the specimens in this section are from PA, and this seems to provide a good case in point. This specimen and the nymph (#766) are good examples of dorothea, and they both came from sections of the Brodheads in the Poconos. The other specimens came from big limestoners and appear to be invaria. Notice that all of the dun and spinner specimens, except for this one, have banded tails (dark markings at the segments). As far as I know, this is not characteristic of the Eastern version of dorothea (E. dorothea dorothea), but it is a trait of invaria.


I've often speculated the same thing as I've seen examples of eastern invaria that look virtually identical to some of infrequens out West. Compare the specimen I posted http://www.troutnut.com/specimen/1013 to this one of Spence's http://www.troutnut.com/im_user_ident/picture_219_large.jpg Any thoughts guys?
ReplyAw Shucks 10 Replies »
Posted by Martinlf on May 19, 2009 in the species Ephemerella invaria
Last reply on Jul 24, 2009 by Martinlf
OK, this is going to seem like a major duh experience for some of you, but the other night I found a sulphur spinner on the door of a bathhouse in a campground I was staying at. Looking for other bugs I then saw a pale nymph shuck on the door. I was totally confused. A nymph this far from the stream? Was this some alien bug? Looking closer I noticed that the shape was too slender for a nymph and that the wing pads were more like little protruding pockets--and it hit me. Spinner shuck. I knew that mayflies molted to produce a spinner, but I had thought the shuck would be more insubstantial--something that would be flimsy and lack form. This was so cool, and at the same time I felt so silly for thinking it could somehow have been a nymph shuck. It's the first spinner shuck I've seen, but I assume that I'll start seeing them everywhere now, like a new word you learn. Anybody else have a spinner shuck story?
Reply
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