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.

Stream photos

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Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington

This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.

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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.

Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Mayfly Genus Penelomax

This recently minted genus contains a single, very distinctive species, Penelomax septentrionalis. Visit that page for information.

Where & when

In 19 records from GBIF, adults of this genus have been collected during June (74%), July (16%), May (5%), and November (5%).

In 4 records from GBIF, this genus has been collected at elevations of 341, 361, 2152, and 2441 ft.

Genus Range

source

Map of specific collection sites

Specimens of the Mayfly Genus Penelomax

1 Female Dun

Female Penelomax septentrionalis Mayfly Dun

10 Pictures

Lateral view of a Female Penelomax septentrionalis (Ephemerellidae) Mayfly Dun from the West Branch of the Delaware River in New York

I'm confident this dun belongs to septentrionalis, because her legs are just too long for any other Ephemerellid, and her unusual mid-dorsal stripe matches those of two easily identified nymphs I collected some miles downstream.

This really pretty mayfly was in kind of bad shape when I found it crippled on the surface, and bouncing around in my container with a bunch of green drakes didn't help.

Collected May 31, 2007 from the West Branch of the Delaware River in New York

Added by Troutnut on June 4, 2007

Collected May 31, 2007 from the West Branch of the Delaware River in New York and added by Troutnut on June 4, 2007

2 Nymphs

Penelomax septentrionalis Mayfly Nymph

3 Pictures

Dorsal view of a Penelomax septentrionalis (Ephemerellidae) Mayfly Nymph from the Delaware River in New York

Collected May 12, 2007 from the Delaware River in New York

Added by Troutnut on May 18, 2007

Collected May 12, 2007 from the Delaware River in New York and added by Troutnut on May 18, 2007

Male Penelomax septentrionalis Mayfly Nymph

12 Pictures

A hairy mayfly nymph. This gangly, odd-looking nymph is from the rare species Ephemerella septentrionalis

Artistic view of a Male Penelomax septentrionalis (Ephemerellidae) Mayfly Nymph from the Delaware River in New York

This is surely the most distinctive-looking species in Ephemerellidae. I like the rugged, spindly look. If mayflies made movies, Penelomax septentrionalis would probably play the supervillain.

Maybe I should take a break and get something to eat.

Collected May 12, 2007 from the Delaware River in New York

Added by Troutnut on May 18, 2007

Collected May 12, 2007 from the Delaware River in New York and added by Troutnut on May 18, 2007

Discussions of Penelomax

Anyone know more about Ephemerella septentrionalis?

11 replies

Posted by Troutnut on May 18, 2007 in the species Penelomax septentrionalis

Last reply on Jul 18, 2011 by Oldredbarn

I found about one sentence on these in Gonzo's book, and haven't seen them mentioned anywhere else in fly fishing literature. Nor is any of the scientific literature I have on them particularly interesting (just descriptions). Now that I've collected a few and see what unique-looking nymphs they've got, I'm really curious about them.

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