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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Case view of a Pycnopsyche guttifera (Limnephilidae) (Great Autumn Brown Sedge) Caddisfly Larva from the Yakima River in Washington
It's only barely visible in one of my pictures, but I confirmed under the microscope that this one has a prosternal horn and the antennae are mid-way between the eyes and front of the head capsule.

I'm calling this one Pycnopsyche, but it's a bit perplexing. It seems to key definitively to at least Couplet 8 of the Key to Genera of Limnephilidae Larvae. That narrows it down to three genera, and the case seems wrong for the other two. The case looks right for Pycnopsyche, and it fits one of the key characteristics: "Abdominal sternum II without chloride epithelium and abdominal segment IX with only single seta on each side of dorsal sclerite." However, the characteristic "metanotal sa1 sclerites not fused, although often contiguous" does not seem to fit well. Those sclerites sure look fused to me, although I can make out a thin groove in the touching halves in the anterior half under the microscope. Perhaps this is a regional variation.

The only species of Pycnopsyche documented in Washington state is Pycnopsyche guttifera, and the colors and markings around the head of this specimen seem to match very well a specimen of that species from Massachusetts on Bugguide. So I am placing it in that species for now.

Whatever species this is, I photographed another specimen of seemingly the same species from the same spot a couple months later.
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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Stonefly Genus Pteronarcys (Salmonflies)

This genus contains the largest stoneflies, and probably the most important thanks to the species Pteronarcys californica. It is commonly called the Salmonfly, and is responsible for the famous hatches of giant stoneflies across the West in the summer. Pteronarcys princeps complements it in higher altitudes across its range.

Pteronarcys dorsata or Giant Black Stone as it is often called is an eastern species which occasionally provides angling action, but it is nocturnal and its populations cannot compare with californica.

In most angling literature, species of this genus were referred to as Salmonflies in the West and Giant Black Stoneflies/Stone Creepers in the East. Over time these regional names are going by the wayside as more and more anglers refer to all of them collectively as Salmonflies.

Read about each species for details.

Where & when

In 55 records from GBIF, adults of this genus have mostly been collected during May (42%), April (25%), June (16%), July (9%), and March (5%).

In 1 record from GBIF, this genus has been collected at elevation of 11007 ft.

Genus Range

Specimens of the Stonefly Genus Pteronarcys

2 Male Adults
3 Female Adults
9 Nymphs

1 Streamside Picture of Pteronarcys Stoneflies:

Discussions of Pteronarcys

High Water
8 replies
Posted by Dbar on Apr 13, 2007 in the species Pteronarcys californica
Last reply on Jun 11, 2017 by Ricofreako
The hatch often occurs during high water (just after peak) so you sometimes have limited visibility during the hatch. Also - I believe that they can occur above 7000 feet.

Love ths site.
Salmonfly question for you westerners
7 replies
Posted by Troutnut on Jul 30, 2006 in the species Pteronarcys californica
Last reply on Jun 4, 2016 by Chipper
I don't have many reliable sources about this species, so it'd be great if you western fishermen could read over the article and make sure I haven't said anything stupid or omitted anything important. I'll be happy to incorporate any additions you have.
7 replies
Posted by Max29 on Jan 29, 2008 in the species Pteronarcys dorsata
Last reply on Jan 29, 2008 by Taxon
Are stoneflies and salmonflies the same thing or are they just related because here in the mid west we have the stonfly hatch and if they are related the stonfly could be called the salmonfly and the salmonfly hatch is only in the west because I have trouble because I want to become a better insect identifier when it comes to fishing because i went to other sites that so a stonefly is a stonefly and a salmonfly is a salmon fly but yet you say stonefly nymph but in parenteseses you have american salmonfly so is there really no such thing as a salmonfly but it is rather called a stonefly.

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Stonefly Genus Pteronarcys (Salmonflies)

Genus Range
Common Name
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