Fly Fishing for Trout Home
User Password
or register.
Scientific name search:

> > Ephemerella nymph

The Specimen

Ephemerella aurivillii Mayfly NymphEphemerella aurivillii  Mayfly Nymph View 11 PicturesThis is a puzzling one to identify and I'm not sure about the species. The maxillary palp (
The palp on the maxilla of an Ephemerella nymph (detached and photographed under a microscope) is highlighted in red here.
The palp on the maxilla of an Ephemerella nymph (detached and photographed under a microscope) is highlighted in red here.
Palp: A long, thin, often segmented appendage which can protrude from certain insect mouth parts such as the maxillae. Also known as the < />palpus.
is present and segmented, and the maxillary canines are not strongly serrate laterally. I think it's Ephemerella, not Serratella. The ventral (Ventral: Toward or on the bottom.) lamellae of the gills on abdominal segment 6 have a clear median notch with a depth at least half the length of the lamellae, which points toward a couple of uncommon species (most likely Ephemerella alleni), but the abdominal tubercles (
A few (not all) of the abdominal tubercles on this Ephemerella needhami nymph are circled.  They are especially large in this species.
A few (not all) of the abdominal tubercles on this Ephemerella needhami nymph are circled. They are especially large in this species.
Tubercle: Various peculiar little bumps or projections on an insect. Their character is important for the identification of many kinds of insects, such as the nymphs of Ephemerellidae mayflies.
and coloration don't fit that species. To add to the confusion, none of the above species are expected to emerge in the fall, as far as I know. I'm going to call this one Ephemerella aurivillii for now, but that's highly uncertain.
Collected September 10, 2020 from the Foss River in Washington
Added to by on September 19, 2020

The Discussion

MillcreekSeptember 24th, 2020, 9:28 pm
Healdsburg, CA

Posts: 352
I think this nymph may be Ephemerella tibialis. I am basing this on the following papers by Allen and Edmunds.

Ephemerella tibialis is in the paper on Serratella.
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
TroutnutSeptember 26th, 2020, 10:53 am
Bellevue, WA

Posts: 2704
I was using this more recent key from Jacobus et al (not sure where to find a PDF online at the moment):

Jacobus, L. M., N. A. Wiersema and J. M. Webb. 2014. Identification of Far Northern and Western North American mayfly larvae (Insecta: Ephemeroptera), north of Mexico. Joint Aquatic Science meeting, Portland, OR. 176 pp. + suppl. Unpublished workshop manual.

Here's the relevant key couplet:

81e) Maxillary canines strongly serrate laterally; thoracic nota with small, brown excrescences (sometimes difficult to detect), especially between forewingpads = Ephemerella (Vittapallia) tibialis (very similar to E. nuda)

81e’) Maxillary canines not obviously serrate laterally; thoracic nota without small, brown excrescences = 81f

I think I did find a number of E. tibialis nymphs earlier this year in Idaho. Here's one of them. I remember being able to make out the highly serrate canines pretty clearly and possibly the excresences, and I couldn't find either one on this specimen. However, I don't have the greatest microscope and am hoping to get a better one soon, so I might take a closer look.

Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

Quick Reply

You have to be logged in to post on the forum. It's this easy:
Username:          Email:

Password:    Confirm Password:

I am at least 13 years old and agree to the rules.

Related Discussions

TitleRepliesLast Reply
Re: Ephemerella tibialis
In Male Serratella micheneri Mayfly Nymph by Millcreek
2Dec 26, 2019
by Millcreek
Re: Brown Dun hatch/swarm time?
In the Mayfly Species Ameletus ludens by Konchu
10Apr 30, 2009
by Troutnut
Re: Mix-up
In Siphlonurus autumnalis Mayfly Nymph by GONZO
2Jul 2, 2011
by Troutnut
Re: Ephemerella dorothea infrequens ?
(2 more)

In the Identify This! Board by Millcreek
25Jan 8, 2016
by Wbranch
Re: Dobsonfly
In General Discussion by FredH
8Mar 28, 2014
by Taxon
Re: Ephemerella maculata
(1 more)

In the Photography Board by Millcreek
3Apr 12, 2015
by PaulRoberts
Re: Serratella micheneri nymphs
In the Photography Board by Millcreek
2Oct 13, 2014
by Millcreek
Re: species taxonomy
In the Mayfly Genus Caudatella by Konchu
3Oct 30, 2010
by Taxon
Re: Ephemerellinae
In the Mayfly Family Ephemerellidae by GONZO
7Oct 4, 2008
Re: Korean Bugs
(2 more)

In the Identify This! Board by FisherOfMen
7Jul 11, 2016
by Gilsau
Most Recent Posts
Re: Pennsylvania Hennies
In Fishing Reports by Martinlf (Partsman replied)
Re: Possible ID
In the Mayfly Species Apobaetis futilis by Sreyadig (Crepuscular replied)
Re: Hennies
In Fishing Reports by Partsman (Martinlf replied)
Re: Gila River Hatch Chart?
In General Discussion by JJTrout (Troutnut replied)
Re: Quick bug collecting and gear test trip
In Site Updates by Troutnut
Re: Are there trout in this stream?
In Beginner Help by Camphammer (Wbranch replied)
Re: First trout of 2021!
In Site Updates by Troutnut (Adirman replied)
Re: How to make a French Coil
In General Discussion by Adirman (Martinlf replied)
Re: Do trout eat Striders?
In General Discussion by Red_green_h (Steamntrout replied)
Walt’s Worm
In Fly Tying by Coha