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The Specimen

Serratella micheneri (Little Western Dark Hendrickson) Mayfly NymphSerratella micheneri (Little Western Dark Hendrickson) Mayfly Nymph View 9 PicturesThis specimen has tarsal claws (Tarsal claw: The claws at the tip of the tarsus, on an insect's "foot.") with 7 denticles (
The denticles on the tarsal claw of this Ephemerella nymph are highlighted in red.
The denticles on the tarsal claw of this Ephemerella nymph are highlighted in red.
Denticle: Small tooth-like projects, often appearing like serrations on the tarsal claws of certain mayfly nymphs.
)
and 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.
)
on abdominal segments 4-7 only. It keys to Serratella micheneri, as do some other specimens from the same collection that lacked the dorsal (Dorsal: Top.) stripe.
Collected July 28, 2019 from Mystery Creek #199 in Washington
Added to Troutnut.com by on July 30, 2019

The Discussion

MillcreekDecember 24th, 2019, 7:31 pm
Healdsburg, CA

Posts: 332
This nymph appears to be Ephemerella tibialis formerly known as Serratella tibialis. Check out Allen and Edmunds; http://www.ephemeroptera-galactica.com/pubs/pub_a/puballenr1963p583.pdf

Also check https://bugguide.net/node/view/696565/bgpage and https://bugguide.net/node/view/876178

Edit: Just noticed the other two Serratella micheneri sets of photos. These also appear to be Ephemerella tibialis.

Also spotted these two sets of photos where you identified the same or a similar nymph as Ephemerella tibialis.

http://www.troutnut.com/specimen/1176

http://www.troutnut.com/specimen/1178
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
TroutnutDecember 25th, 2019, 8:19 pm
Administrator
Bellevue, WA

Posts: 2549
I keyed this one under the microscope using a more recent key than Allen and Edmunds:

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.

The couplet on page 64 distinguishes E. tibialis from the other species:

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


If I'm remembering correctly (and I might not be), I looked pretty hard at the maxillary canines and the thoracic nota under the microscope and couldn't find the characteristics pointing to tibialis. It is a bit odd that I didn't mention that in the captions, though, so perhaps I'm misremembering or I just failed to interpret the characteristics correctly.

The key does describe Serratella as having "Abdominal terga either without tubercles or with relatively large, blunt and somewhat sinuate tubercles", and one of the other specimens I labeled as micheneri seems to have sharper tubercles than those shown in the corresponding illustration in the key.

Perhaps Luke can weigh in?
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
MillcreekDecember 26th, 2019, 8:01 am
Healdsburg, CA

Posts: 332
Found these pictures at Bold. They're not very good quality but may give enough to identify the critters.

http://v3.boldsystems.org/index.php/Public_SearchTerms?query=%22Serratella%20micheneri%22[tax]

http://v3.boldsystems.org/index.php/Public_SearchTerms?query=%22Ephemerella%20tibialis%22[tax]

It would be nice to hear from Luke.
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein

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