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Mayfly Family Ephemerellidae (Hendricksons, Sulphurs, PMDs, BWOs)

Taxonomic Navigation -?-
Kingdom Animalia (Animals)
» Phylum Arthropoda (Arthropods)
» Class Insecta (Insects)
» Order Ephemeroptera (Mayflies)
» Family Ephemerellidae (Hendricksons, Sulphurs, PMDs, BWOs)
Genus in EphemerellidaeNumber of SpecimensNumber of Pictures
Attenella528
Caudatella00
Dannella00
DrunellaBlue-Winged Olives860
EphemerellaHendricksons, Sulphurs, PMDs120529
EurylophellaChocolate Duns1569
Penelomax222
Serratella16
Teloganopsis00
Timpanoga00

2 genera aren't included.
Common Name
Pictures Below
The Ephemerellidae are probably the most important family of mayflies for the American trout angler. Most of the species known as Hendricksons or Sulphurs belong to the genus Ephemerella in this family, while the genus Drunella lays claim to the large eastern Blue-Winged Olives and the Western Green Drakes.  

Where & When

A curious property of this family is that the males and females often inhabit different parts of the stream. In many species the males and females are of different sizes and colors, it your fly may need to match the main gender emerging from your stretch of the river.

Hatching Behavior

These are fantastic dry-fly insects. Behavior varies by species, but almost all have excellent qualities for the angler. Some emerge laboriously in the surface film, where emerger and floating nymph patterns are excellent. Others emerge on the bottom, during their rise to the surface, or immediately subsurface; most of these species are good wet fly fare and they take a very long time to dry their wings once they reach the surface. There they ride like sailboats in classic mayfly style, fluttering occasionally, and are imitated by classic mayfly patterns.

Many species are especially prone to being 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.
)
or crippled, and trout are especially fond of this wounded prey and our crafty imitations.

Spinner Behavior

Most species return to the stream as spinners one day after they emerge. Spinner falls are usually concentrated over the riffles.

Nymph Biology

Environmental Tolerance: Most species are unusually tolerant of silt, warmth, and pollution. Some, like Ephemerella subvaria, are not.
Nymphs of this family are a gift to the angler, because many have the peculiar habit of swimming up and down between the surface and the bottom several times before actually emerging. I do not know what actual biological purpose these seeming "practice runs" serve, but they expose the slow-swimming nymphs to the trout.

Several authors, including , write that some of the nymphs crawl to the high tips of rocks and other objects prior to emergence, where they may be picked off their perches by peckish trout. In my experience photographing the nymphs underwater in April, they often graze in such exposed locations even when they aren't about to emerge.

Between their tendency to be in exposed places, the unsure footing of some species in fast water, and behavioral drift (Behavioral drift: The nymphs and larvae of many aquatic insects sometimes release their grip on the bottom and drift downstream for a while with synchronized timing. This phenomenon increases their vulnerability to trout just like emergence, but it is invisible to the angler above the surface. In many species it occurs daily, most often just after dusk or just before dawn.), the nymphs of this family are important to trout year-round.

165 Mayfly Specimens in the Family Ephemerellidae:

Specimen Page:1234...18
Ephemerella subvaria (Hendrickson) Mayfly DunEphemerella subvaria (Hendrickson) Mayfly DunView 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.
Region: Catskills
Collected Apr 19, 2006
Added Apr 22, 2006
Drunella tuberculata Mayfly DunDrunella tuberculata  Mayfly DunView 14 PicturesI don't know for sure that this is Drunalla tuberculata, but that's my best guess for now.

It certainly has a different look and much more robust body shape from Drunella lata duns I photographed a couple weeks earlier, so I doubt it's that species. Using distribution records to eliminate other choices narrows this down to Drunella tuberculata or Drunella walkeri.

Markings described for the abdominal sternites (
One sternite of this Isonychia bicolor mayfly spinner is highlighted in red.
One sternite of this Isonychia bicolor mayfly spinner is highlighted in red.
Sternite: The bottom (ventral) part of a single segment on an insect's abdomen.
)
of the male spinner of Drunella tuberculata are suspiciously similar to those on this female dun. Also, this dun is 9.5mm long (my ruler pic isn't very good, but I'm basing this on measuring the real thing). The size range given in the old Allen & Edmunds keys for walkeri females is 7-8mm, while tuberculata is 9-11mm. For these reasons I'm sticking it in tuberculata for now.

This is the only Drunella mayfly I saw all day. I scooped it off the water as it emerged at around 7pm from a big Catskill tailwater.
Region: Catskills
Collected Jun 1, 2007
Added Jun 8, 2007
Ephemerella subvaria (Hendrickson) Mayfly SpinnerEphemerella subvaria (Hendrickson) Mayfly SpinnerView 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.
Region: Northeast
Collected Apr 23, 2007
Added Apr 25, 2007
Specimen Page:1234...18

9 Streamside Pictures of Ephemerellidae Mayflies:

Streamside Photo Page:12
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Here's an above-the-water view of a stillborn Ephemerella subvaria dun which I also photographed from below the water.
Here's an above-the-water 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 dun which I also photographed from below the water.

In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
RegionUpper Midwest
Date TakenApr 19, 2006
Date AddedApr 23, 2006
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RegionNortheast
Date TakenApr 30, 2007
Date AddedMay 3, 2007
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This Ephemerella invaria sulphur dun got stuck in its shuck trying to emerge.  This isn't exactly a "natural" pose for a photograph, but it kind of shows what an emerger pattern could look like.
This Ephemerella invaria sulphur dun got stuck in its shuck (
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.
)
trying to emerge. This isn't exactly a "natural" pose for a photograph, but it kind of shows what an emerger pattern could look like.

In this picture: Mayfly Species Ephemerella invaria (Sulphur).
RegionUpper Midwest
Date TakenMay 20, 2007
Date AddedJun 6, 2007
Streamside Photo Page:12

37 Underwater Pictures of Ephemerellidae Mayflies:

Underwater Photo Page:12345
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This Ephemerella subvaria (Hendrickson) nymph picture is one of my favorites.
This Ephemerella subvaria (Hendrickson) nymph picture is one of my favorites.

In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
RegionUpper Midwest
Date TakenMar 24, 2004
Date AddedJan 25, 2006
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There's a large Ephemerella subvaria nymph in the top left.
RegionUpper Midwest
Date TakenMar 20, 2004
Date AddedJan 25, 2006
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The mayfly and stonefly nymphs in this picture blend in extremely well.
The mayfly and stonefly nymphs in this picture blend in extremely well.

In this picture: Insect Order Plecoptera (Stoneflies) and Mayfly Species Ephemerella invaria (Sulphur).
RegionUpper Midwest
Date TakenMar 20, 2004
Date AddedJan 25, 2006
Underwater Photo Page:12345

Recent Discussions of Ephemerellidae

PMD Spinner - Egg sack color? 5 Replies »
Posted by Wbranch on Jan 26, 2010 in the species Ephemerella excrucians
Last reply on Jan 27, 2010 by Taxon
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.
ReplyDrunella in the Smokies 6 Replies »
Posted by Konchu on Sep 20, 2009 in the species Drunella tuberculata
Last reply on Jan 4, 2010 by Konchu
Just got back from a trip to the North Carolina side of the Smokies. Drunella tuberculata (probably the conestee form) is getting ready to hatch there. Most of the other bugs of decent size that I saw were relatively young.
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?
ReplyLearning to Use the Force 6 Replies »
Posted by Martinlf on Jun 18, 2009 in the genus Serratella
Last reply on Jun 23, 2009 by Martinlf
Went over to the Dark Side the past two days. Thanks to all who helped. By the way, Jason, fished spinners also.
ReplyEmerger 6 Replies »
Posted by Martinlf on Jun 10, 2009 in the genus Serratella
Last reply on Jun 12, 2009 by GONZO
Does anyone know the color of the emerging/freshly emerged dun?
Reply
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