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 Ephemerellidae |  |  |
| Attenella | 5 | 28 |
| Caudatella | 0 | 0 |
| Dannella | 0 | 0 |
| DrunellaBlue-Winged Olives | 8 | 60 |
| EphemerellaHendricksons, Sulphurs, PMDs | 120 | 529 |
| EurylophellaChocolate Duns | 15 | 69 |
| Penelomax | 2 | 22 |
| Serratella | 1 | 6 |
| Teloganopsis | 0 | 0 |
| Timpanoga | 0 | 0 |
2 genera aren't included.
Common Name
| Match | Common Name |
 | Hendricksons, Sulphurs, PMDs, BWOs |
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 (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.
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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:
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.
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.Region: Catskills
Collected Apr 19, 2006
Added Apr 22, 2006
Drunella tuberculata Mayfly Dun
View 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 (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.
View 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 (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 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.
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.Region: Northeast
Collected Apr 23, 2007
Added Apr 25, 2007
9 Streamside Pictures of Ephemerellidae Mayflies:
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Here's an above-the-water view of a stillborn (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).
In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
This Ephemerella invaria sulphur dun got stuck in its shuck (
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).
Here's an underwater view of the pupal shucks of several already-emerged Brachycentrus numerosus caddisflies.
In this picture: Mayfly Species Ephemerella invaria (Sulphur).
37 Underwater Pictures of Ephemerellidae Mayflies:
This Ephemerella subvaria (Hendrickson) nymph picture is one of my favorites.
In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
There's a large Ephemerella subvaria nymph in the top left.
In this picture: Insect Order Trichoptera (Caddisflies), Mayfly Species Ephemerella invaria (Sulphur), and Mayfly Species Ephemerella subvaria (Hendrickson).
In this picture: Insect Order Trichoptera (Caddisflies), Mayfly Species Ephemerella invaria (Sulphur), and Mayfly Species Ephemerella subvaria (Hendrickson).
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).
In this picture: Insect Order Plecoptera (Stoneflies) and Mayfly Species Ephemerella invaria (Sulphur).
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?
ReplyThere are 15 more topics.
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