Artistic view of a Male Pteronarcys californica (Pteronarcyidae) (Giant Salmonfly) Stonefly Adult from the Gallatin River in Montana

Salmonflies
Pteronarcys californica

The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.

The trees were leafing out and the trout were rising on this productive Wisconsin stream

From the Namekagon River in Wisconsin

Stream photos

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Ephemerella mucronata Mayfly Nymph Ephemerella mucronata Mayfly Nymph

Dorsal view of a Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington

This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.

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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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Lepto question

This topic is about the Mayfly Family Leptophlebiidae

The champions of this family are Leptophlebia and Paraleptophlebia, along with the relatively newly-defined genus Neoleptophlebia containing several important species that were once in Paraleptophlebia. The large mayflies of Leptophlebia are on the water sporadically for a long time. The Paraleptophlebia and Neoleptophlebia flies are smaller but come in much more concentrated numbers.

Leptophlebiidae also contains several genera and species which are never mentioned in fly-fishing literature, either because they are too rare or because they require water too warm for trout.

Example specimens

10
Neoleptophlebia Mayfly Nymph

Dorsal view of a Neoleptophlebia (Leptophlebiidae) Mayfly Nymph from the Yakima River in Washington

This nymph keys pretty well to Neoleptophlebia. Under the microscope, the fork on the first gill is more symmetrical than it looks in the picture here. Following the species key in Jacobus et al. (2014), the lack of tusks on the head or postero-lateral spines on segment 8 leads to adoptiva or heteronea, but both refer to a 3-segmented labial palp as a key characteristic, and this one only seems to have two segments, just like another, different-looking specimen from the same sample. So I'm stuck. I thought the end of the abdomen of this one was damaged during capture and transport, but I photographed it anyway because it looked different from the others. However, it became clear under the microscope that it was actually just mid-way through molting and the abdomen was intact underneath. I got a couple nice microscope photos showing that. The pattern of markings on the abdomen is still distinctive compared to the other specimen, which was more representative of a common nymph in my sample. This one was unique.

6
Neoleptophlebia Mayfly Nymph

Dorsal view of a Neoleptophlebia (Leptophlebiidae) Mayfly Nymph from the South Fork Snoqualmie River in Washington

10
Neoleptophlebia Mayfly Nymph

Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.

JasonM
Prescott, AZ

Posts: 1

JasonM on Mar 6, 2010March 6th, 2010, 7:18 pm EST

I live in Arizona and I have a question...

Over the past several years I have witnessed a spectacular emergence of mayflies on a stream I frequent in the Mogollon Rim area of Arizona. The stream is a tributary to the Little Colorado River drainage.

The adults seem to emerge on exposed midstream rocks of along the shoreline. The duns can be very dense, sometimes every rock along shore has one drying its wings beforetaking flight They are a dark greyish brown bodied, dark grey winged adult, I have named them MOCHA DUNS for lack of knowledge of their true identity. Three tails on the adult as well. They are pretty big....a big size 14 to 16. I have captured several specimens as larvae that I believe are the same species as the ones I have observed as adults. The larvae have prominent gills. 3 long split tails, similar size and color, hign densities along shore and in the shallows, etc. I'm 90% sure that they are Leptophlebiidae. But I don't know the species, yet.

The trout don't seem to key in on the adults...since they emerge on land...but I have experienced some incredible fishing during very windy days while the hatch is on. The nymphs appear to have trouble holding on to the substrates they are trying to emerge on. I have witessed several swimming to a streamside cobble, grasping the rock for a moment, only to be swepped back into the water by small, lapping waves being caused by the wind. They try repeatedly but seem to get exhausted pretty quickly. They must be easy picking for fish cruising along the bank, as I have great success fishing imitations along the shore with short twitches. I have rarely seen duns on the surface of the stream, even on the windiest of days. They seem to emerge late morning to early afternoon.

CAN ANYBODY SUGGEST WHAT SPECIES THIS MAYBE. I don't have a scope or any literature anymore. I have experience with ID'ing but not lately

Any help would be appreciated by this inquisitive angler. Thanks

Jason Mszaros
The Drag Free School of Fly Fishing
928-273-9445

howdy

Taxon

Site Editor
Plano, TX

Posts: 1311

Taxon on Mar 6, 2010March 6th, 2010, 7:45 pm EST

JasonM-

What month of the year does this emergence seem to peak?

If it's some time between mid-June and mid-July, my guess would be Paraleptophlebia memorialis.

Here is a detailed description:

Family: Leptophlebiidae
Scientific name: Paraleptophlebia memorialis

Previously know as: Leptophlebia memorialis, Leptophlebia pallipes (in part), Paraleptophlebia pallipes
Common name: Mahogany Dun, etc.
Locality: W
CAN Regions: NW
MEX Regions: SW
USA Regions: NW, SW
Cent. Amer. Countries:
CAN Provinces: AB, BC.
MEX States: BN.
USA States: AZ, CA, CO, ID, NM, OR, SD, UT, WA
Habitat:
Voltinism:
Emergence (begin) date: mid-Jun
Emergence (end) date: early-Aug
Emergence time of day: afternoon
Spinner fall time of day:

Nymph minimum length: 6 mm.
Nymph maximum length: 7 mm.
Nymph identification keys: gill fork 1/3 from base; abdominal spines on segment 8 & 9; tergites dark, each w/three light dots, a medium-sized one on center-line, and a small-sized one forward on each side of center-line
Nymph body description:
Nymph legs:
Nymph gills: gill/filament length ratio (1:3), trachael branching: (absent)
Nymph tusks: absent
Nymph tails: 3,

Dun minimum length: 6 mm.
Dun maximum length: 8 mm.
Dun identification keys:
Dun body description: brown to dark reddish brown
Dun wings: medium gray, hind wings w/o costal angulation
Dun legs: brown
Dun tails: 3, light to dark brown

Spinner minimum length: 7 mm.
Spinner maximum length: 7 mm.
Spinner identification keys: male claspers w/3 joints
Spinner body description: abdomen whitish
Spinner wings: hyaline, fore wing with attached intercalaries, hind wing w/o costal angulation
Spinner legs:
Spinner tails: 3,

Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com