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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
Baetis

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.

Dorsal view of a Neoleptophlebia (Leptophlebiidae) Mayfly Nymph from the Yakima River in Washington
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.
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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Mayfly Genus Paraleptophlebia (Blue Quills)

There are many species in this genus of mayflies, and some of them produce excellent hatches. Commonly known as Blue Quills or Mahogany Duns, they include some of the first mayflies to hatch in the Spring and some of the last to finish in the Fall.

In the East and Midwest, their small size (16 to 20, but mostly 18's) makes them difficult to match with old techniques. In the 1950s Ernest Schwiebert wrote in Matching the Hatch:

"The Paraleptophlebia hatches are the seasonal Waterloo of most anglers, for without fine tippets and tiny flies an empty basket is assured."

Fortunately, modern anglers with experience fishing hatches of tiny Baetis and Tricorythodes mayflies (and access to space-age tippet materials) are better prepared for eastern Paraleptophlebia. It's hard to make sense of so many species, but only one is very important and others can be considered in groups because they often hatch together:
In the West, it is a different story. For starters the species run much larger and can be imitated with flies as large as size 12, often size 14, and rarely smaller than 16. Another difference is the West has species with tusks! Many anglers upon first seeing them think they are immature burrowing nymphs of the species Ephemera simulans aka Brown Drake. With their large tusks, feathery gills, and slender uniform build, it's an easy mistake to make. Using groups again:

Where & when

In 191 records from GBIF, adults of this genus have mostly been collected during July (27%), June (25%), August (16%), May (12%), September (9%), and October (5%).

In 54 records from GBIF, this genus has been collected at elevations ranging from 3 to 9751 ft, with an average (median) of 896 ft.

Genus Range

Hatching behavior

Though usually noted for migrating to the shallows to hatch, most species at times emerge in classic mayfly style on the surface and ride the water for a while before flying away. This is exacerbated by the inclement weather they often hatch in. Floating nymph patterns and emergers are very effective at these times. The hatch may last for a few hours each day.

George Edmunds in Mayflies of North and Central America documented that Paraleptophlebia mayflies have been observed to emerge by crawling out onto shore when the water is high in the Spring, but since he gives no further details about which species do this it is reasonable to assume it's generic. Knopp and Cormier note in Mayflies: An Angler's Study of Trout Water Ephemeroptera the same behavior.

Spinner behavior

Time of day: Weather dependant

Habitat: Soft margins

According to Edmunds, the females will mate more than once and often proceed to shoreline foliage when finished with ovipositing as opposed to dying spent on the water. The males start the swarms first, often well before. They are often observed along the shoreline dipping from six to two feet and rising again. On occasion, many males for unknown reasons drop to the water at this time and become trapped in the meniscus. When the females finally arrive, they join them quickly at the top, copulate during the four foot fall, and just as quickly make short dives to either dip their abdomens into the water or land on the water to lay their eggs. Then it's up and back at it until they're finished. Edmunds reports that they will repeat this cycle as many as three times before they occasionally die spent on the water or more often head back to the bushes. This is good information for the angler to note.

Nymph biology

Current speed: Moderate to fast

Substrate: Sand, gravel, detritus

Although classified as crawlers, Paraleptophlebia nymphs look more like little burrowers (especially the tusked variety) and swim very well. They are generally tolerant of faster water than Leptophlebia and inhabit pockets in riffles as well as moderate runs.

Specimens of the Mayfly Genus Paraleptophlebia

2 Male Duns
5 Female Duns
4 Male Spinners
5 Female Spinners
5 Nymphs

1 Streamside Picture of Paraleptophlebia Mayflies:

Discussions of Paraleptophlebia

Western Paraleptophlebia
17 replies
Posted by Entoman on Feb 4, 2012
Last reply on Feb 7, 2012 by Entoman
Paul wrote in another topic:

Yes, the Paraleps can come about the same time as the tricaudatus, but don't start as early I think. And I think they were a mid-morning deal where tricaudatus has more of an afternoon peak. (Here in the rockies we're not supoosed to don't have the early P adoptiva, although last spring I found a single youngish nymph that my key would only take it to adoptiva -by gills if I remember right. Wish I'd pickled it and had it properly ID'd.

Anyway, back east I found the Paraleps emerged from slower currents and siltier substrates -often along stream edges. Whereas tricaudatus spilled out of the riffles. They could mix of course in certain places, but one could find one predominant if you wanted to (and I did bc I wanted to know each better), by focusing on key habitat.

Fly patterns could be identical really, although I had my own, esp for the nymphs. In fact, I'm still using some P adoptiva mimic parachutes (more a dun gray) during Baetis activity.

I largely agree, though they seem to be more tolerant of current than most genera of leptophlebiids. I have sampled them from riffles. In my experience (with an admitted western bias), they are far more important in the Fall. If an angler is lucky enough to be in place (and aware of them) when they are schooled up in preparation for hatching, some memorable nymphing can take place! :)

P. adoptiva is an eastern species. By far the most important species in the West is P. debilis, though they can be found mixed with others, particularly the unusual tusk bearing species bicornuta and in some locales packii. Anglers that occasionally come across these tuskers often confuse them with the immature burrowing ephemerids they resemble. Many anglers use their standard nymphs and do just fine with them. The PT is a popular pattern. Sometimes, a nymph that more accurately suggests their silhouette is the ticket. Because of their build and very obvious gills, they look more like a small long-tailed burrower than they do the typical baetid or ephemerellid, and it is good for the angler to keep this in mind.

Most duns and spinners are typically a rich brown, hence the name "Mahogany Dun." They can run the gamut from gray to almost black though, depending on the location. The slender bodies and coloration of the duns lead to them often being mistaken for baetids, but the oval vertically held hind wings and three tails make them easy to distinguish from that family. Check out this link to the hatch page for a look at the natural dun.
http://www.troutnut.com/hatch/752/Mayfly-Paraleptophlebia-debilis-Mahogany-Dun

Below are a couple of patterns I find very useful when this critter is about.

Mahogany Dun Nymph #16



Mahogany Paradun #16


Paralep Hatching Behavior
9 replies
Posted by Shawnny3 on Apr 6, 2009
Last reply on Apr 29, 2009 by Taxon
I can't remember where I read or heard these things (might have been on this site), but I want to make sure my vague recollections are not totally false. When Paraleptophlebia are mating, do they make exaggerated dives in clouds above the stream? If so, do they often end up in the water at these times or do they fall as spinners much later? Finally, when they emerge, do they do so at the stream bottom and then swim to the surface as duns?

Thanks for any help,
Shawn

Start a Discussion of Paraleptophlebia

References

Mayfly Genus Paraleptophlebia (Blue Quills)

Taxonomy
11 species (Paraleptophlebia altana, Paraleptophlebia aquilina, Paraleptophlebia cachea, Paraleptophlebia calcarica, Paraleptophlebia jeanae, Paraleptophlebia jenseni, Paraleptophlebia kirchneri, Paraleptophlebia placeri, Paraleptophlebia quisquilia, Paraleptophlebia sticta, and Paraleptophlebia traverae) aren't included.
Genus Range
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