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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Lateral view of a Female Sweltsa borealis (Chloroperlidae) (Boreal Sallfly) Stonefly Adult from Harris Creek in Washington
I was not fishing, but happened to be at an unrelated social event on a hill above this tiny creek (which I never even saw) when this stonefly flew by me. I assume it came from there. Some key characteristics are tricky to follow, but process of elimination ultimately led me to Sweltsa borealis. It is reassuringly similar to this specimen posted by Bob Newell years ago. It is also so strikingly similar to this nymph from the same river system that I'm comfortable identifying that nymph from this adult. I was especially pleased with the closeup photo of four mites parasitizing this one.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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This topic is about the Mayfly Genus Ephemerella

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.

Example specimens

bedminster, nj

Posts: 4
Jpsully on May 23, 2008May 23rd, 2008, 1:22 am EDT
Hey Jason:

There are some beautiful photos posted on that forum under the "Fishing" section, and titled "Bugs are cool". My guesses as to ID are: first 2 pics (same fly)- Stenacron (orange tint, two tails, mottled wing and banded femur), third pic - Ephemerella Attenella (3 tails, slate wings and faded olive body), last 2 pics (same fly) would appear to be Maccafertium (Grey Fox - not March Brown) based on 2 tails and light coloration. Am I correct in my assumptions? Any help you could provide would be appreciated. Thanks.

Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on May 23, 2008May 23rd, 2008, 2:17 am EDT

Just in case you'd like another (unsolicited) opinion while you're waiting for Jason's response, I'd say you've got it about right. Here's what I see:

1st mayfly (female dun)--probably Stenacron interpunctatum. It's a bit hard to see the telltale Stenacron wing marking in the photo, but it sure looks like it.

2nd mayfly (female dun)--could be Attenella attenuata (or Drunella lata). You may see the former in older texts as Ephemerella attenuata and the latter as either Ephemerella cornuta or Drunella cornuta. (Both of these could be hatching now. Size might help. If it's ~ 10mm, it's probably lata--later season hatches of lata are smaller. If it's ~ 8mm, it's probably attenuata.)

3rd mayfly (male dun)--Maccaffertium vicarium. This used to be split into March Brown (Stenonema vicarium in older texts) and Grey Fox (Stenonema fuscum in older texts), but both are now under M. vicarium.

I hope that helps.
bedminster, nj

Posts: 4
Jpsully on May 23, 2008May 23rd, 2008, 3:29 am EDT

Thanks, that is definitely helpful. You are right on with your details.
Just what I was looking for.

Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on May 23, 2008May 23rd, 2008, 3:31 am EDT
My pleasure, JP.
Softhackle's profile picture
Wellsville, NY

Posts: 540
Softhackle on May 24, 2008May 24th, 2008, 1:45 am EDT
Nothing to do with your flies, JP, but where in blazes have you been?

"I have the highest respect for the skilled wet-fly fisherman, as he has mastered an art of very great difficulty." Edward R. Hewitt

Flymphs, Soft-hackles and Spiders: http://www.troutnut.com/libstudio/FS&S/index.html

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